论文部分内容阅读
用固定化酶法已能大量地将青霉素G或V转化为6-APA,但用酶法大量地将头孢菌素C转变为γ-ACA则尚未成功.由产黄青霉菌、顶头孢霉菌、小小棒状链霉菌及诺卡氏菌等产生青霉素、头孢菌素和头霉素共有八个生物合成反应步骤,每一步都有选择性的酶和特殊辅酶参与才能促进反应进行.第一步:由ACV合成酶使L-α-氨基己二酸(A),L-半胱氨酸(C)和L-缬氨酸(V)连成所有青霉素和头孢菌素中间体的前体,即三肽化合物(LLD-ACV).第二步:由异青霉素合成酶将LLD-ACV氧化,环化为异青霉素N,加入Fe~(2+)和维生素C,可促进反应.第三步:经异青霉素N异构化酶使之差向异构为青霉素N.第四步:通过脱乙酰氧头孢菌素C合成酶及Fe~(2+)、维生素C和α-酮戊二酸
Penicillin G or V has been converted to 6-APA in large quantities by the immobilized enzyme method, but the enzymatic conversion of cephalosporin C to γ-ACA in large quantities has not been successful yet, and Penicillium chrysogenum, Small penicillium and Nocardia penicillin, cephalosporin and cephamycin a total of eight biosynthetic reaction steps, each step has a selective enzyme and special coenzyme in order to promote the reaction.First step: L-a-aminoadipic acid (A), L-cysteine (C) and L-valine (V) are linked by ACV synthetase into precursors for all penicillins and cephalosporin intermediates, namely Tripeptide compound (LLD-ACV) Step 2: Isopenicillin synthase oxidizes LLD-ACV, cyclizes to isopenicillin N, and adds Fe 2+ and vitamin C. Step 3: Is isopenicillin N isomerization enzyme epimerization to penicillin N. The fourth step: deacetoxycephalosporin C synthase and Fe ~ (2+), vitamin C and α-ketoglutaric acid