Abstract

The bioconversion of D, L-20aminothiazoline-4-carboxylic acid (D, L-ATC) to L-cysteine was investigated. After the intracelluar enzyme of a Pseudomonas species was inducibly formed by addition of D, L-ATC in the middle of culture, the cells were isolated and treated with sonication to prepare the crude enzyme solution. The results indicated that the cysteine was produced only in the form of L-isomer from D,L-ATC and its production could be enhanced several tens times by addition of managanese ions which were required as a cofactor in this enzymatic reaction. Bedies, this reaction suffered from the feedback inhibition of L-cysteine. On the other hand, since L-cysteine-decomposing enzyme coexisted in the crude enzyme solution, most of the L-cyseine formed disappeared in the absence of its inhibitor. However, hydroxylamine was found to be a potent inhibitor which could successfully prevent the decomposition of L-cyseine.

D,L-2-aminothiazoline-4-carboxylic acid(D,L-ATC)로 부터 L-cysteine으로의 bioconversion에 대한 특성을 살펴보았다. Pseudomonas species의 배양중에 D,L-ATC를 첨가하여 균체내에 그 관여되는 효소를 유도, 생성시키고 균체만을 모은 후 파쇄하여 조효소액을 제조하였다. 실험결과, DL-ATC로 부터 L-형의 cysteine 만이 생성되며, 이 반응에 관여되는 효소는 cofactor로서 Mn이온을 필요로 하며, Mn 이온의 첨가에 의해 L-cysteine의 생성량이 수십배 증가되었다. 그러나, 이 효소는 생성물인 L-cysteine에 의해 feedback inhibition을 받았다. 한편, L-cysteine의 분해효소가 조효소액 내에 존재하며 그 효소반응의 저해제없이는 생성된 L-cysteine의 대부분이 분해되었다. 반면, 매우 효과적인 효소저해제인 hydroxylamine의 첨가로 L-cysteine의 분해를 거의 방지할 수 있었다.

Keywords

• L-cysteine;
• D,L-ATC;
• bioconversion