The Chemical Modification of Biopolymers. III. The Introduction of SH Groups into Taka-amylase A

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Abstract
The enzymic activity of Taka-amylase A on amylose, as measured by the blue-value method, increased to 180% of the original when one mole of mercaptosuccinyl group was introduced into one mole of the enzyme. Similar results were obtained for the activity measured by the Semogyi-Nelson method; the introduction of one or two mercaptosuccinyl groups raised the activity to 130–140% of that of the native enzyme. Even after the attachment of six mercaptosuccinyl groups per mole, the activity was 120% of the original. However, the enzymic activity was not elevated, but was lowered, by succinylation. When the sulfhydryl groups of the mercaptosuccinyl groups were blocked with p-chloromercurybenzoate or iodoacetamide, the enzyme was inhibited. These results suggest that the sulfhydryl groups of mercaptosuccinyl residues play an important role in increasing the enzymic activity.