[Choice of a spin label probe in order to study the recombination of beta-hydroxybutyrate dehydrogenase of a rat liver inner mitochondrial membrane with lecithin vesicles].

We find from studying the inhibitory effect of N-ethylmaleimide (NEM) on the enzymatic activity of beta-hydroxybutyrate dehydrogenase, that approximately one molecule of NEM is bound for one molecule of protein when the enzymatic activity is completely inhibited. Since the protein is a dimer this implies that each molecule of protein possesses only one thiol group in its catalytic center. Two long chain maleimide derivates: (10.3) NEM and (1.14) NEM conform, if a reasonable assumption is accepted to the conditions required for the study of the recombination of beta-hydroxybutyrate dehydrogenase with lecithin vesicles by spin label technique.