Col1agen Syrnposiurn， VI (1965) 97

コラーゲンの生合成の機序について

紺野邦夫ぺ手 塚統夫料

(*昭和大学医学部生化学教室;料千葉大学医学部生化学教室)

コラーゲンはどんな特徴をもった壷白か?

コラーゲンの生合成を他の蛋白合成と区別して考えることの裏には， コラーゲγが他の蛋白

といろいろの点でひどく異なっているので， その生合成も他の蛋白のそれとは異なっているか

も知れないという期待があるからであろう. どのような点が異なっているか，生合成に関係の

あるものだけをあげて見ると:

1)コラーゲンは分子量の大きな線維状蛋白質であるが，その構成アミノ酸は限られたもの

であること，その中でも結晶部分を構成するアミノ酸配列は Gly-Pro-Xのくりかえしと考えら

れること.

2)アミノ酸}組成では他の蛋白に見られないオキシプロリンが10%前後も見出されること，

遊離のオキシプロリンは結合には入らないこと.これらはオキシリジンについても同様である.

3)コラーゲンの分子はX線解析の結果では三本のペプチド鎖から出来たラセシ構造をもっ

ているという.この中でオキシプロリンの -OHは全てラセ γの内側を向いているか，逆に全て

外側を向いているかのどちらかだという.

4)コラーゲンには抗原性がない.

以上の特徴は種や臓器によらず共通している.

5 )コラーゲンは糖蛋白であるとされている. その末端はN一端， c一端共に遊離していない

という.

6 )コラーゲンは発生のある時期，創傷の治癒時など， 限られた場令にのみ合成がさかんと

なる.アスコルビン酸欠乏や副腎皮質ホノレモ γ投与はこれを妨げるようにイ力らくという.

一般の霊白合成機構ては説明がつかないか?

つかないことはない.コラーゲンは 1つのリボゾームの上で出来ると考えては大きすぎるが，

Rich et al.のいうようなポリゾームを仮定すれば説明はつく.その他の， 合成を起し，終ら

せ，また阻害する因子については，一般機構の方がまだ分っていないので何ともいえない.

特殊な蛋自の合成機構ゼ上と異なるものはあるか?

ある.それは細菌の壁物質の生成である. ここで用いられるアミノ酸はグリシ γ， アラニシ

など限られており， c-端， N-端とも遊離しておらず， その合成にはRNAは不要であり，ベニ

シリシ，ゲンチアナ紫などによって阻害をうける.

コラーゲン合成のさかんな組織はどうしたら得られるか?

我々が採用したのはラット背部皮下に寒天を植える法である. 1 ~ 2週後， 寒天周囲の膜を

検鏡すると，ほぼ純粋に線維芽細胞の集まりであることが認められる.令 文献上，肉芽腫を作る

ために使われている物質はすべてポリアニオシである.

98

この肉芽腫lまinvitroゼコラーゲン走合成するかどうか?

肉芽腫を挽肉状にして C14ーアミノ酸とインキユベートした後，冷TCAで蛋白を沈殿させ，数

回洗って遊離アミノ酸を除く.熱TCAでコラーゲγを抽出し， 冷アセト γを加えて沈殿させ，

とりこまれたアミノ酸の放射能を測定する.少なくも 4時間まで， このとりこみは直線的であ

り，酸素，エネルギー源としての基質の存在はとりこみを著しく高める. 挽肉状にした肉芽腫

を音波処理してソニケートを作る.このソニケートも，熱TCAで抽出される分画にアミノ酸を

とりこむが，それは無機リンの添加によって促進され， RNase，クロラムブエニコーノレの添加で、

は阻害が著明でなく，ヒアノレロニダーゼ，ベニシリ γの添加は阻害的で、あった.

細胞内のどの分画がこのとりこみにあずかるのか?

肉芽腫を持ったラットにC14ーアミノ酸を腹腔内注射し 3時間後， とり出してソニケートと

し分画遠心を行ない，各分画の比活性をしらベた. またソニケートの各分画を作り，これを

C14ーアミノ酸を含むメヂウムとインキユベートした後， コラーゲン分画をとり比活性を見ると

いう， in vitroの実験も行なった.いずれの場合でも比活性のもっとも高いのは， 8，500 x g ，30

分の遠心で沈殿する分画で，大頼粒と考えられた. この分画は，上清を加えなくてもアミノ酸

をとりこむ能力があり， とりこまれるアミノ酸の割合も， グリシγ3モルに対しプロリ γ2.3

~2.5モルでコラーゲ γの組成に近く， また熱 TCA;抽出分画の放射能はコラゲナーゼ処理で高

率に遊離してくることなどから，この頼粒がコラーゲγを合成していると考えられよう.

大頼粒の本体はなにか?

8，500 x g， 30分の遠心でおちる頼粒として才ーに考えられるのは， ミトコシドリアである.

電子顕微鏡によって肉芽腫中にも典型的なミトコシドリアの存在が確められたが， 8，500 x g沈

殿分画にはそれらしいものは見当らない. 東糖濃度勾配遠心法によってもこの大頼粒とミトコ

シドリアとは別のものであることが確められた. 蚕の後部絹糸腺で同様の大頼粒が認められて

いるが，その詳細はなお研究中と言ってよい. 次に考えられるのはボリゾームである.これは

阻害剤の効果や大頼粒の核酸含量などからただちに同ーのものとは考えられない.

細菌の壁物質との関係はあるだろうか?

上に述べた阻害剤の効果からコラーゲシは壁物質に近いメカニズムで合成されるのではない

かとの予想、も生れる. しかし仔細に検討すると， ペニシリン，ゲシチアナ紫などは 1mMでは

ほとんど無効で， 7~8mMではじめてある程度阻害する. ATPの添加はそれ程でないのに，

エネルギー源の添加効果は著しい.洗機した大頼粒では， ヒアノレロニダーゼの阻害効果が幾分

落ちるなど，壁物質と呉なった点が多いのに気附く.

按酸代謝の面からの接近

あらかじめp32を注射してから，一定時間後に肉芽腫をとりただちに凍結，酸溶性分画をとっ

て分析した.肉芽腫のコラーゲシ合成がさかんな春・夏に於ては常に 2におよび 3'ーヌクレオシ

ド・モノリ γ酸のピークが 4つ認められた.

その量的割合いはA=U，G= CおよびA: G=10: 16~17であり， いわゆるDNA-タイプ

である.P32は1時間以降ここに現われ，5'ーヌクレオチドの比活性に対する2'-，3'-ヌクレオチド

の比活性は時間と共に増加する.コーチゾンで前処置しておくとこの増加はかなり速かになる.

一方コーチゾ γ処理後の核のRNA量およびp3ZのRNAへのとりこみは，著しく増加し，対照

の数倍になることもある. 処理後12時間程すると， 大頼粒分画のアミノ酸とりこみが促進され，

数倍になることもある.

99

大頼粒分画にlま按酸が含まれるか?

正常肉芽腫の場合の薦糖密度勾配遠心では，大頼粒部に一致してp32のごく小さな山がある.

遠心にかける前のソユケートをヒアノレロニーダーゼで処理しておくと p32の山はかなり大きく

なる.8，500X雪上清をヒア/レロニダーゼ処理して密度勾配遠心にかけると，大頼粒が再び現わ

れて来る.なおコーチゾγ処理した大頼粒の糖質は半減しているのが認められた.

現段階ゼコラーゲンの生合成をどう考えるか?

以上の結果から，我々はまず細胞内のコシパートメ γテーシヨシを考えたい.核内のDNAはコラーゲシ構造に関する情報をになっており， これはアニオ γで活性化されカチオンで、阻害さ

れる.これから情報をうけたRNAや合成の場としてのリボゾームは， おそらくヒアノレロ γ酸で

出来た被膜に包まれて核からはなれ， 中でコラーゲγ分子を作りつつ細胞膜に近ずいて行く.

不要になったRNA，リボゾームは被膜の外へ捨てられる. 最後に出来上ったコラーゲシ分子は

ミグロソーム上で水酸化をうける.

ブロリン→オキシプロリンの変換はどのようにしてお己るか?

我々の実験では，遊離オキシプロリシは入らない.プロリ γのオキシプロリシへの変換は8，500

xg上清に於てよく見られる，およびこの変換はかなりゆっくり進行する. 文献に見られる種

々の実験をすべて認めるならば， この水酸化反応はミクロソーム上で起り，その基質特異性は

かなり低いものと考えられる. しかしコラーゲシのペプチド鎖はかなり速かに出来るので，プ

ロリノレ-s-RNAのような中間体はオキシプロリンの有力な前駆体とはなり得ず， おそらく二重

または三重のらせん構造が出来上った後，水酸化が起るのであろうと考えられる. 従って，オ

キシプロリ γの-OHらせんの外側をむいているモデルを支持したい.

100

Studies on the Connecti ve Tissue

III. Biosynthesis of Collagen by the Granuloma Tissue in vitro

Kunio Konno * and Tsunao Tetsuka林

(* Department of Biochemistry， Showa University School of Medicine ;

** Department of Physiological Chemistry， Chiba University Medical School)

Col1agen is a unique protein in the animal kindom. A major part of this protein

consists of a repeating unit， Gly-Pro-X， which gives rise to a peculiar X-ray diffrac-

tion pattern[) and one-third of the amino acids in this protein is accounted for by

glycine and one-tenth each by proline and hydroxyproline. The content of aromatic

amino acids is very low， and the sulfur-containing amino acids are presentin insig-

nificant amounts2l. Proline， rath巴rthan fr巴ehydroxyproline， appears to be the major

precursor of hydroxyproline in col1agen3，4l.

If the mechanism of synthesizing collag巴ninvolves amino acid activation of amino-

s-RNA and its transfer to the ribosomal “messenger RNAヘitis to be expected that

a collagen-synthesizing system can be prepared in a way similar to that generally

used for the biosynthesis of other prot巴ins.

This report is concerned with the synthesis of collagen in preparations from

granuloma induc巴dby the agar-implantation into rats， and the hydroxylation of

bound proline in collagen.

EXPERIMENT AL

Matherials: Th巴 granulomas used in these experiments were obtained by the

method reported previously， using male albino rats weighing 120 to 200 g2l.

Glycine-2-C14 was a product of Dai-ichi Pure Chemicals Co. (1. 5mcJmmole);

proline-1-C'4 was purchased from Nuclear Chicago Coゆ. (DL-form， 2.7mcJmmole).

Tritium-labeled proline and hydroxyproline， preared by the Wilzbach's method 5)， were

the kind gifts of Dr. Tsurufuji of the Faculty of Pharmaceutical Sciences of this

University and of Dr. Komai of the National Institute of Health in Tokyo， respectively.

The mixture of C'4-amino acid was an acid-hydrolyzate of Chlorella protein， a gift

of the Fifth Laboratory of the Institute of Applied Microbiology， University of Tokyo.

Hyaluronate lyase [EC 4.2.99.1) was the product of Mochida Phαrmaceutical Co. ;

Ribonuc1ease (RNase) [EC 2.7. 7.16J， deoxyribonuc1ease (DNase) [EC 3.1. 4. 5J and

c1ostridiopeptidase A [EC 3.4.4. 19J (previously called as collagenase) were the products

of W orthington Biochemical Corρ. Crystalline trypsin [EC 3. 4. 4. 4J was “Trypur" of

Novo Co.， and muramidase [EC 3.2.1. 17] (previously called as‘lysozyme') was the

101

gift of Prof. D. Mizuno of the Faculty of Pharmaceutical Sciences of this University.

Hyaluronic acid was prepared by the m巴thodof Dorfman and Cifonelli6).

Methods : In the experiments with slices the granuloma was excised and its capsular

portion was minced and used. If not otherwise specified， the granuloma was used two

weeks after the agar-implantation.

In the cell-free experiments， the minced tissue was suspended in 5-6 volumes of

a solution composed of O. 05M phosphate buffer， pH 7. 4， O. 2M sucrose， O. 0078M MgS04，

O. 02M KCl， treated for 20 minutes with sonication (9 KC)， and the nuc1ear fraction，

fiber and the undisintegrated kelp were sedimented by centrifuging at 800 x g for 10

minutes. Collagen was extracted by the method of Fitch et al. 7)

To remove the contaminating free G14-amino acid， the preparation was washed

5-8 times with 5 % TCA containing carrier.

Radioactivity was determined with a window-less gas-f1ow counter using Q gas as

quenching gas at an operating vo1tage of 1200. The materials were plated on stainless

planchets as infinitely thin layer. The materials plated were around 1 mg. The deter-

mination of tritium was run by using a Packard Tri-Carb liquid scinti11ation counter.

Collagen was hydrolysed by heating in 6N HCl in sealed tube at 105"C for 18-20

hours. Proline and hydroxyproline were iso1ated by descending paper chromatography

in butano1-acetic acid-water (4 : 1 : 2).

RESULTS

Amino acid incorporation into collagen : The time course of the incorporation of

glycine-2 _(14 into collagen in the minced granu10ma tissue is shown in Fig. 1. Under

these experimental conditions， i. e. ， without any oxidizable substrate， the addition of free

hydroxyproline appears to affect the level of C14-incorporation after the first hour of

incubation， thus confirming the findings of Daughaday and Mariz8).

Tab1e 1 shows that the better conditions for the glycine incorporation into collagen

are at the neutral pH， aerobiosis and the presence of ascorbic acid. Thc latter was

rep1aced by other oxidizab1e substrate without accompanying the decrease of incorpo・

ration (Tabl巴II).

Anaerobiosis remarkab1y decreased the incorporation of glycine-2-(14. In the case

of th巴 additionof hya1uronate 'lyase， the increased incorporation is considered to be

due to an increased accessibi1ity of amino acids to the “site" of collagen biosynthesis.

Incorporation of proline and hydroxyproline into collagen Stetten conc1uded

that the major precursor of collagen hydroxyproline was pro1ine which was hydroxy1ated

in its “bound" form4). However， other interpretations may a1so be 巴ntertained，

becaus巴 herexperiment was performed in vivo. Here， the degradation of hydroxy-

proline is very rapid in liver， 80 there is a possibi1ty that the inj巴ctedhydroxyproline

does not reach the site of collagen synthesis. Green et al. assured Stetten's conc1usion by

2 o

!i "-

102

5叶お 1~ .!主 15トU ー孟8

5ぞ10"'E

b号室)← 4

2

。

""

Hydro~yproline (+川

副yd問 yproline(ー)I

Fig. 1 Incorporation of glycine-C14 into collag巴nin minced g釦ra官加a紅印n山lbuffer，pH 7.4; 0.85% NaCl; amino acid mixture (Moriamin S)， 18mg; glycine-2-C14 ， 1μc; final volume 3 ml， minced ti詰sue，300mg). Final concentration of hydroxyproline was 0.0067M. 3TC.

O

釜 ot 1 2 ーよ一一上一一一一」234

Table 1

Aerobic

Anaerobic

T J ME (hours)

Requirements for the amino acid incorporation into collagen

V.C. (ー)

6.4

3.4

P出 5 pH7.4

|いV C lに;:二:f:f;1 ¥三:f二f斗コιゾ二IH)町山1む3(+(-) (+)lyaωse

5.2 10.3 19.8 32.1

3.7 6.3 7.2 6.7

N. B. 1) Medium-0.013M phosphate buffer ; 0.85% KCl; amino acid m凶 ure(Moriamin S) 9mg; glycine-2-C14， 1μc; volume 3ml 2) Ascorbic acid， 0.0侃1M;hy戸屯叫alurona凶a抗tely戸r屯as問e5印O∞O仰Fμtg/v刊es鉛s記剖el.Amount 0ぱfm凶in配ce吋dtissue

was ca. 100 mg wet weight per vessel. Incubation was carrid out at 370C for 2 hours with agitation. Then， TCA containing carrier glycine was added. This washing was repeated 8 times， and the collagen fraction was extracted by the method of Fitch et al. 3) The values are expr明日edas c. p. m. per mg coIlagen.

their in vitro experiment9l， while Mitoma reported that free hydroxyproline might

be also incorporated into fetal collagen， although to a lesser extent10) than proline.

The present authors examined this possibility of direct incorporation of hydroxy-

proline in vitro. The resu1t is shown in Fig. 2， i. e.， free H"-hydroxyproline is not

incorporated into collagen and the addition of 02-hydroxyproline does not affect the

incorporation of 04_prolin巴 intototal collagen， if the system contains enough oxidizable

substrate.

Biosynthesis of collagen in a cell free system A cell-free preparation was

obtained from granuloma material by sonication.

This sonicate was capable of promoting the incorporation of amino acids into

collagen and the incorporation was stimulated by the inorganic phosphate and decreased

appreciably by the addition of gentian violet (pararosani1ine) and hyaluronate lyase

in the presence of phosphate buffer， and less so by chloramphenicol and RNase

(Table III).

The hyaluronate effect contradicts the findings in the experiments with minced

103

Table 11 Effect of the oxidizab!e substrates for the amino acid incorporation into collagen

Radioactivity c.p.m./mg collagen

None O2 23.8

Succinate "63.2

Exp. 1 日 -Ketog!utarate 73.6

Citrate 47.2

Ma!ate 59.8

Succinate O2 19.2

G!ucuronate 22.1

Exp. 2 G!ucosamine 11.0

Hya!uronate 17.4

Hya!uronate !yase 64.2

N2 2.8

Gas phase Substrate added

O.OlMpfiosphate buffer， pH 7.4; 0.85% KC!; 4x10・'MA!CJ，; g!ycine-2-C14， 1μc; the

fina! concentration of the added substrate was 0.55M. Vo!ume 3m!. Incubation with

minced tissue was carried out at 370C for 2 hours.

N.B.

g

t;一一一一一一 一一一一一一円<{

乏ft:<{-

岩51コベ255叶もp言 1u...==ri， O凶巨 l

E五¥'日里 10<x:n-o E 豆、d

EたE E Llr <'3こ

ヱ

O

/ +Hyd roxyprol ine-C 12

同pv

au h//

o

t

r

pι

戸一川

Hydroxyproline-H3

~

Fig. 2 Incorporation of pro1ine and hydroxypro1ine into collagen in the minced granu!oma tissue (Krebs-

Ringer phosphate buffer， pH 7.0， 3.0m!; 0.5M sodium succinate， 0.3m!; 0.77 M r、~aC! ， 0.2m!;

amino acid mixture (Moriamin S)， 9 mg; C14-

proline or H'-hydroxyproline， 0.3μc). Fina! concen-tration of C12_proline and C12-hydroxypro!ine was

0.3mM.

tissue. In a cell free system， amino acids access to the site of col1agen biosynthesis

without degradating the mucosubstances.

Amino acid incorporation by subcellular fractions: The following experiment was

designed to provide information as to the site of collagen biosynthesis. One granuloma

was sonicatecl and fractiona.tecl as ip Sch~rne 1， 3 h01，lr旨 aft~r th~ intraperitopea1 adrni-

104

Table 111 Amino acid incorporation into coIlagen by a ceIl-free system

Tris pH 7.4 I Complete system -ATP + Hdase +RNase +Pi

Exp. 1

2

14.8

18.5

9.4

16.5

12.4

24.4

11. 3

39.7

5

184

140

159

OL

び

3a

N

D

+

e

nb a

間十c

p

十Phosphate buffer I Complete 十CMsystem

Exp. 3

4

O

O

63

N. B. 1) Abbreviations used are PC (penicillin)， CM (chloramphenicoI)， Hdase (hyaluronate lyase) and GV (gentian violet). Final concentrations of PC，CM and GV were 7.8 and 8mM in Exp. 3，4 and 1 mM in Exp.5. In Exp. 5， Hdase (500μg) was used with 7 mM PC. Concentrations of RNase， DNase and mmamidase were)20~150μg/ml

throughout the experiments. In Exp. 2， the final inorganic phosphate concentration was 6.7mM

2) Medium for Exp. 1 and 2: Tris-HCl buffer (pH 7.4)， 0.155M; DL-proline-1-C14， 0.5μc; amino acid mixture (final concentration of each amino acid was 1 mMwithout PI・oIineand hydroxyproline); ATP， 1mM; MgS04， 1.5mM; KCl， 0.85%; sodium succinate， 0.05M; volume， 3 m!. Incubation at 370C for 2 hours. Medium for Exp. 3-5: phosphate buffer (pH 7.4)， 0.067 M; C14司algal-proteinhydrolyzate， 5μc; ATP，

2mM; MgSO， ， 10mM; cytochrome c， 6.7μM; sodium pyruvate， 15mM; volume 3m!. Incubation at 370C for 2 hours.

nistration of the C14-amino acid mixture into a granuloma-bearing rat. Each fraction

of the granuloma sonicated， which was from non-injected rat， was incubat巴d in a

medium containing glycine-2・C14for 17 and 18 hours.

Under in vivo as weIl as under in vitroふ conditions，the sp巴cificactivity in the hot

TCA-extractable fraction was the highest iIl the large particulate fraction (M and

P16 in Table IV). p-Chloromercuribenzoate (5x.1O-'M) inhibited completely the incor司

poration in vitro.

The amino acid incorporation into collagen by the large particulate fraction

After the incubation of the sonicate from either a one week or two week granuloma

with O'-amino acid mixture， ice-cold 0.25M sucrose containing non-labeled amino

acids (in concentrations 100 times greater than those of the labeled amino acids used)

was added， and the large particulate fraction and th巴 supernatantwere separated by

the centrifugihg at 8，500 x g for 30 minutes. Trichloroacetic acid precipitates were

prepared from each fraction， washed five times with trichloroacetic acid， and th巴ir

radioactivity determined.

The change of the specific radioactivity in each fraction with time is shown

in Fig.3. The washed partictilate fraction was also able to incorporate amino acids

into the coIlagen fraction (Table V and VI). In the large particulate fraction， the

flmino acid incorporation was inhibited by the addition of penicil1in or hyaluronate

105

lyase (Tabl巴 VI).

Some properties of collagen formed in the Iarge particle: We reported previously

that the hot TCA-extractable fraction from the granuloma was thought to repres巴nt

mainly col1agen2九 althoughthis had not yet been ascertained rigorously. We found

that the incorporation of OCamino acids was not affected by the addition of crystalline

trypsin (150μg/ml) to the incubation medium， but that the specific activity of the

hot TCA-extractable fraction increased to more than twice that of the control. After

gelatinization， trypsin treatment rendered the radioactive material soluble in 70%

ethanol， while treatment with diluted alkali， RNase or hyaluronate lyase did not

change the solubility of this material. In case of treatment with clostridiopeptidase

A (col1agenase)， the change in solubility was more marked than that obtained with

trypsin， in that 50-70% of the radioactivity was found in the 80% acetone-soluble

fraction*.

Electron microscopic observation on the granuloma and the large particulate

fraction: The site of protein biosynthesis in the granuloma cells (almost all of them

Scheme 1

Fractionation procedure for in vivo and in vitro experiments for amino acid incorporation

(A) Fractionation for the experiments of in vivo incorporation (B) Fractionation for the incorporation experiments in vitro

(A) (B)

Granuloma Granuloma

Sonication Sonication

800xg，10 min

Ppt Super

I N I 8，500xムー一H一

1，000xg，10 min

Super

10，5000x g，60 min

Super Ppt

m此削川，0刈O∞O∞μO

Super Ppt

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*In the case of the collagenase digestion of authentic col1agen， the major part of the 80% acetone-soluble fraction consisted of tripeptides which had a glycine as an amino-termina residue and also contained either one proline or hydroxyproline residue (unpublished data).

106

Table IV (A) Amino acid incorporation into subcellular fractions in vivo

N 乱f問

hdH

P

P

S

r… 70.6 18.3 45.9 TCA precipitate

c.p.m./mg 726 1400 1245 1105 978

(Total…ight m 29.5 5.5 11.3 12.1 34.3 Collagen fraction

c.p.m./mg 559 1013 707 790 384

(B) Amino acid incorporation into collagen by subcellular fractions in vitro

Exp. 1 I H(OOC) H N P16 S16

c.p.m./mg collagen 18.8 910 749 3500

c.p.m./g connective tissue 5500 640 4350 2825

Exp. 2 P16 S16 P16+ρCMB IS川ーCMB

c. p. m. /mg collagen 42000 11800 85 54

N.B. ]) Notations in the Table are the same as in Scheme 1. 2) TCA concentration : Final 5 %， N， M， P， pH 5， S， TCA precipitate mean the pre-

cipitates which were precipitated by 5 % TCA at each step of fractionation. 3) (A) : C14・Algalprotein hydrolyzate 100μc was administered intraperitoneally in the

granuloma-bearing rat. After 3 hours， the granuloma was removed and fractionated as shown in Scheme I-(A). (B) : The granuloma was removed and fractionated， and each fraction was incubated in the followi四 mediumat 370C for 17 hours (Exp. 1) and 18 hours (Exp. 2).

Phosphate buffer (pH 7. 4)， 0.03M; glycine-2・Cl'，1，uc; amino acid mixture (Moriamin S)， 18mg; ATP 0.6mM; MgSO， 1mM; nicotinamide 0.6mM; sodium succinate O. 01M and volume 5-6 ml.

were found to be fibroblasts) was assumed to be the large particulates. Electron

microscopy revealed the presence of well-developed membraneous structure in the

granuloma cel1 (Fig.4-A) and electron-dense partic1es in the sedimented pel1et after the

centrifugation with 8，500 x g for 30 minutes (Fig. 4-B).

Conversion of peptide-bound proline to hydroxyproline: If the polypeptide synthe-

sized were col1agen itself， it would be expected that the incorporated pro1ine residues

would be hydroxylated. After the incubation of the large partic1es with C1cproline，

the collagen fraction was extracted from it， hydrolyzed with 6 N HCl， and the hydroly-

zat巴 subjectedto paper chromatography. Proline and hydroxypro1ine were eluted after

the separation and their respective radioactivity was determined (Table VII). The

same collagen fraction was also re-incubated with th巴 S85fraction* at 370

C for 16 hours

*S85 was used as a notation for t)1e supernatant fr司ctionafter the çentrifu~ation wit)1 8，500 x g， _ fQr $0 mint¥tes，

107

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Table V Amino acid incorporation into collagen hy the subcellular fractions

C"-Pro

Fraction 8，500 x g， sediment

1 week-granuloma

2 week-granuloma 557

957

387

13

8

N.B. Phosphate buffer (pH 7. 4) ，containing 0.067M MgSO，; O.OlMKCI; 0.06M cytochrome Cι; 6x 10'6リMn凶1吋icotinamide引 10mMNAD; 0.3mM NADP; 0.15mM A乱MP; 5mM G乱MP;5 日mMGMP;Cυ" 一t叩a訂叩n凶I

m犯町cir祉r町mmoω1，2.7mcimmol respectively); in one week granuloma， ascorbic acid O.OlM; in 2 week granuloma， sodium succinate 0.05M; total volume 3 ml， 37OC， 2 hours incubation

in the presence of penicillin and chloramphenicol (300μg /ml)- The procedure after

the second incubation was the same as employed after the first incubation. As shown

in Table VII， the eonv巴rsionof proline to hydroxyproline appears to continue during

the second incubation， as evidenced by the hydroxyproline ratio.

DISCUSSION

Collagen biosynthesis is markedly increased during some period of embryonic life，

in the course of wound healing and at the site of foreign body reactions. In such

108 Table VI Effects of various inhibitors on amino acid incorportion into

collagen by the large particulate and supernctant frcction

| Large 凹 ricuI山 f凶 ion(8，500xg，間diment)

卜丸 町J0 time

Exp. 1 I c. p. m. /mg. colIagen

2 I c.p.m./mg. colIagen

3 I c.p.m./mg. collagen

Exp. 1 I c. p. m /mg colIagen

" 2 I c. p.m /日19 collagen

3 I c. p.m /mg collagen

8，500 x g， supernatant

86

1450

733

N. B. The values at zero time in these experiments were rather high due to the unhydrolyzed portion of the C"-algal protein hydrolyzate used.

(A) (B) ‘-ergastoplasm or endoplasmic reticllll1m electron dense pal'ticlf'

mltochOndna vesicular particule electron-dense particle

Fig. 4 Electron micrograph of the granuloma tissue (A) and the large particulate f:'action sedimented

with 8， 500x g for 30 minutt's (B). fil¥ation was clone by use of 2 % osrllic acicl containing

Y(!l'on'll buf fer，

109

Table VII Conversion of incorporated proline to hydroxyproline

Exp. No. Proline Hydroxyp川 Hp(/%P) ro c.p.m. c.p.m.

Without incubation I 1 365 16.7 4.6

2 60.7 4.0 6.6

Incubated with S" I 123 25.3 20.5

2 196 41. 3 21.1

1 65.0 16.0 24.6

2 44.3 22.3 50.2

N.B. The substrates in these experiments were the collagens fraction obtain巴din the exper-iments shown in Table V. To these collagen fraction， Krebs-Ringer phosphate buffer (pH 7.4)， containing MgSO， and KCl， 0.5ml 0.114M sodium ascorbate， 0.2ml; S" 2・2可tion，O.lml.; penicillin， 300μg/ml ; at 370C for 16 hours. Isatin positive spots of 6.0-9.6 cm from the origin for proline and 1.5-4.9 cm for hydroxyproline were eluted and their radioactivities measured.

cases， it has been reported that many particles app巴arin th巴 fibroblastsω.Kajikawa

c1arified electron-microscopicaUy that the particles were identical with ergastoplasm山 .

Lowther et al.13) and Peterkofsky et al.14

-17) assumed that the site of collagen

biosynthesis was the microsome because the highest specific activity of hydroxyproline

was found in this fraction.

Our results suggest that heavier particles than the microsomes were the most

active in the peptide-bond formation， while the hydroxylation activity appeared to be

involved in the S85 fraction. Protein synthesis in the rat liver mitochondria was

reported by Truman and Kornerl8) and Suttiel9) who found that this reaction was c10sely

dependent upon the oxidative phosphorylation and resistant to RNase action.

Protein synthesis in our large particles in the granuloma was found to be dep巴ndent

upon the presence of oxygen， inorganic phosphate and an oxidizable substrate， and

was less resistant to RNase and chloramphenicol action than the biosynthesis of the

other proteins. How巴ver，the electron aicroscopic observation revealed few mitochon-

dria in the large particulate fraction. Miura etα1. reported that fibroin biosynthesis

in the posterior silk gIands was localized in the large particles which could be

separated from mitochondria by the use of sucrose density gradient centrifugation2Ol.

Here also， chloramphenicol lacked inhibitory activity， but dinitrophenol was a strong

inhibitor. Recently， Rich et al. clarified the role of poly(ribo)somes in biosynthesis

of hemoglobin in reticulocytes21l.

All these data suggests that the large particles found to be active in the synthesis

of collagen in our experiment may be similar to the polysomes or the large partic1es

in silk glands. The Iater case is similar to that of collagen in that fibroin is also a

fibrous protein， although its ap1ino acid composition differs fro}11 ttCl，t Qf collagen，

110

The mechanism of hydroxylation of proline and lysine is unique in the biosynthesis

of collagen. A1thol1gh the hydroxylation mechanism was c1arified by Fujimoto and

Tamiya22l， the step at which the hydroxylation occurred was not finally demonstrated

as yet. Manner and Gould reported the formation of hydroxyproline and soluble RNA

complex by chick embryo and they assumed that the hydroxylation might occur at or

before this step23). Dal1ghaday and Mariz fOl1nd free hydroxyproline with the highest

specific activity when cartilage was incubated with C14-proline and supposed the pre-

sence of an active intermediate of proline8).

However， the time course of the hydroxylation obs巴rvedin our experiments ap-

peared to rule out these hypotheses postulating intermediates. The experimental data

of Peterkofsky and Udenfri巴nd15，17) seem to agree with our results. At this stage of

the investigation， we would like to suggest that the hydroxylation may occur in

substrates of a rather wide range of specificity such as in double or triple stranded

peptide chains which may be only the true precursor of the collagen molecule.

SUMMARY

The mechanism of collagen biosynthesis was investigated 的 vitroby using the

granuloma induced by agar implantation.

In the experiments， the incorporation of labeled amino acid into collagen increased

linear1y up to 4 hours. Free hydroxyproline was n巴verincorporated inte collagen

by this system. Requirements for the incorporation were the presence of oxygen，

inorganic phosphate and oxidizable substrate.

In a cell-free system the amino acid incorporation into collagen was also observed.

It was found that the active fraction of carrying out this incorporation consisted of

large partic1es sedim巴ntedon centrifuging at 8，500 x g for 30 minutes. RNase and

chloramphenicol had only a slight inhibitory effect on this incorporation， but p-chloro-

mercuribenzoate (10-引の inhibitedstrongly. Hyaluronat巴 lyase，gentian violet (7-

8mM) and penicillin (7-8mM) also inhibited a moderate degree of activity.

Electron micrographs of the large partic1es reveal巴dthe presence of many electron-

dense partic1es which were different from typical mitochondria.

The hydroxylation of proline appeared to occur after proline was incorporated into

peptide chains.

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4) Stetten， M. R.， lbid.， 181， 31 (1949)，

111

5) Wilzbach， K. F.， j. Am. Chem. 50c.， 79， 1013 (1957).

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