Polymorphism of rat gastric mucosal histidine decarboxylase: effects of the coenzyme and sulfhydryl groups
Savany, A.; Cronenberger, L.
Biochemistry International 17(2): 345-357
1988
ISSN/ISBN: 0158-5231 PMID: 3190728 Document Number: 322197
Several factors are examined for their implication in the charge heterogeneity and form conversion of rat gastric mucosal histidine decarboxylase. The apoenzyme and the holoenzyme are undistinguishable with respect to their pI and to the distribution of enzyme activity in the three forms. The latter are not produced by differential coenzyme binding. Studies for glycoprotein characterization provide evidence that the heterogeneity does not arise from enzyme-bound carbohydrate. Oxidative or reducive environments changes the distribution between forms without modifying the molecular weight. Conversion of form III to forms I and II can be effected by treatment with dithiothreitol. A similar loss of negatively charged form occurs upon ageing and is not prevented by an alkylating agent. All three forms show equal sensitivity to N-ethylmaleimide and dithiothreitol inhibitions. The oxidation-reduction state of exposed sulfhydryl groups may be responsible at least in part for the charge heterogeneity.