酶法合成头孢环己二烯

以环己二烯甘氨酸甲酯盐酸盐为酰基供体，7-氨基脱乙酰氧基头孢烷酸为酰基受体，γ－氧化铝为载体的固定化巨大芽孢杆菌胞外青霉素G酰化酶为酰化剂，合成了头孢环己二烯。5％酰基供体，2％酰基受体，每毫升反应物加44IU固定化酶，pH7．5，25℃振荡反应5h，头孢环己二烯产率为81％。苯乙酸、苯氧乙酸和头孢霉素G对酶法合成有不同程度的抑制作用。

ENZYMATIC SYNTHESIS OF CEPHRADINE

Cephradine was synthesized by gamma-alumina-immobilized form of the penicillin G acylase of Bacillus megaterium with D-phenyglycine methylester hydrochloride (CH DGME.HCl) as acyl donor and 7-aminodeacetoxycephalosporanic acid (7-ADCA) as acyl acceptor. 0.1 g of 7-ADCA was dissolved by adding 2.5 ml of distilled water and about 0.25 ml of 2 mol/L NaOH in a 25 ml flask. To the solution, after 0.25 g of CHDGME.HCl was added, 0.1 mol/L phosphate-0.05 mol/L citric acid buffer, pH 7.5 was added to result in a volume of 5 ml with pH 7.5 Then 1 g(220 IU) of immobilized enzyme was added. The flask was shaken on a rotary shaker at 110 r/min and 25 degrees C for 5 h. The conversion rate of 7-ADCA was 81%. In an expanded experiment in 500 ml of reactive volume, 11.8 g of cephradine was obtained from 10 g of 7-ADCA. The conversion rate of 7-ADCA was 80% with about 87% yield of cephradine. Enzymatic synthesis was inhibited in varying degrees by phenylacetic acid, phenoxyacetic acid and cephalosporin G.