Abstract
By means of amperometric mercurimetric titration, the -SH groups of native and oxidized sweet potato β-amylase have been determined.
Although eight titratable -SH groups were found in the native enzyme molecule, no distinction between essential and non-essential -SH groups was observed. A partially active enzyme after treatment with o-iodosobenzoate was crystallized by salting out with ammonium sulfate, and only an extensively oxidized one from water upon dialysis. The oxidized enzyme did not restore its activity upon treatment with sodium thioglycolate. Oxidation by iodine was also carried out from which it was presumed that the oxidation of the enzyme either by o-iodoso-benzoate or by iodine does not proceed through the “all or none” mechanism, and also that the essentiality of -SH groups would rather be indirect.
