Sazykin A Iu, Krylov A S, Navashin S M
Antibiotiki. 1984 Nov;29(11):810-4.
beta-Lastamase with the molecular weight of 32500 was isolated from the cells of clinical strain 6803 of Enterobacter aerogenes and purified. By the substrate profile determined microiodometrically beta-lactamase was classified as belonging to the cephalosporinase type. The activity of the electrophoretically homogenous enzyme was equal to 430 microM a minute per mg protein with respect to benzylpenicillin. The Km for benzylpenicillin, dicloxacillin, cephaloridin and cephalothin was 6.5410(-5), 3 X 10(-4), 2.1 X 10(-5) and 5.7 X 10(-5) M, respectively. The isoelectric point of the enzyme equal to 5.45 was estimated with the method of preparative isoelectrofocusing. The presence of the serine residue or residues was shown with the use of selective reagents applied to the functionally important groups. With the method of circular dichroism the ratio of alpha- and beta-structures in the enzyme molecule was determined, the slow hydrolysis of cephazolin was demonstrated and the values of Km and Kcat for this process were estimated.
从产气肠杆菌临床菌株6803的细胞中分离并纯化出分子量为32500的β-内酰胺酶。通过微量碘量法测定的底物谱，该β-内酰胺酶被归类为头孢菌素酶类型。相对于苄青霉素，电泳纯酶的活性为每毫克蛋白质每分钟430微摩尔。苄青霉素、双氯西林、头孢菌素和头孢噻吩的米氏常数分别为6.54×10⁻⁵、3×10⁻⁴、2.1×10⁻⁵和5.7×10⁻⁵M。用制备性等电聚焦法估计该酶的等电点为5.45。使用针对功能重要基团的选择性试剂显示了丝氨酸残基的存在。用圆二色性方法测定了酶分子中α-和β-结构的比例，证明了头孢唑林的缓慢水解，并估计了该过程的米氏常数和催化常数的值。
