[Sensitivity of D-beta-hydroxybutyrate dehydrogenase to proteolytic enzymes; influence of phospholipids]

Controlled proteolysis of D-beta-hydroxybutyrate dehydrogenase in different forms were carried out using several proteases with different and well known specificities. The results obtained were the following: Purified apoBDH (phospholipid-free) was rapidly and strongly inactivated by all proteases tested except leucine aminopeptidase , in contrast with non-membrane enzymes which were unaffected by all proteases. BDH activity was completely preserved when proteases were incubated with either native BDH (membrane linked) or reconstituted BDH with reactivating-phospholipids (lecithins of total mitochondrial phospholipids), while non-reactivating-phospholipids gave no protection against proteases. C-terminal part of the enzyme was found to be essential for enzymatic activity while the N-terminal aminoacid is N-substituted. Controlled proteolysis whatever the protease used (except leucine aminopeptidase ) was followed by strong inactivation of the enzyme.