The enzyme penicillin G acylase (PGA) is not adsorbed at pH 7 on DEAE- or PEI-coated supports, neither is it adsorbed on carboxymethyl (CM)- or dextran sulfate (DS)-coated supports. The surface of the enzyme was chemically modified under controlled conditions: chemical amination of the protein surface of carboxylic groups (using soluble carbodiimide and ethylendiamine) and chemical succinylation (using succinic anhydride) of amino groups. The full chemical modification produced some negative effects on enzyme stability and activity, although partial modification (mainly succinylation) presented negligible effects on both enzyme features. The chemical amination of the protein surface permitted the immobilization of the enzyme on CM- and DS-coated support, while the chemical succinylation permitted the enzyme immobilization on DEAE- and PEI-coated supports. Immobilization was very strong on these supports, mainly in the polymeric ones, and dependent on the degree of modification, although the enzymes still can be desorbed after inactivation by incubation under drastic conditions. Moreover, the immobilization on ionic polymeric beds allowed a significant increase in enzyme stability against the inactivation and inhibitory effects of organic solvents, very likely by the promotion of a certain partition of the organic solvent out of the enzyme environment. These results suggest that the enrichment of the surface of proteins with ionic groups may be a good strategy to take advantage of the immobilization of industrial enzymes via ionic exchange on ionic polymeric beds.

译文

:青霉素G酰基转移酶(PGA)在pH 7时不吸附在DEAE或PEI包被的载体上,也不吸附在羧甲基(CM)或硫酸葡聚糖上(DS)的载体上。酶的表面在受控条件下进行了化学修饰:羧基的蛋白质表面化学胺化(使用可溶性碳二亚胺和乙二胺)和氨基的化学琥珀酰化(使用琥珀酸酐)。完全的化学修饰对酶的稳定性和活性产生了一些负面影响,尽管部分修饰(主要是琥珀酰化)对两种酶的特征影响可忽略不计。蛋白质表面的化学胺化使酶固定在CM和DS涂层的支持物上,而化学琥珀酰化使酶固定在DEAE和PEI涂层的支持物上。这些酶的固定化非常强,主要是在聚合的载体上,并且取决于修饰的程度,尽管在剧烈条件下孵育灭活后酶仍可以解吸。而且,固定在离子聚合物床上使得抵抗有机溶剂的失活和抑制作用的酶稳定性显着增加,这很可能是由于有机溶剂的一定分配的促进。这些结果表明,利用离子基团富集蛋白质表面可能是利用工业酶通过离子聚合床上的离子交换固定化酶的一种好策略。

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