ADP-regenerating enzyme systems in mitochondria of guinea pig myometrium and heart

The role of hexokinase (HK) and adenylate kinase (AK) enzyme systems in the synthesis of adenosine 5'-diphosphate (ADP) was analyzed in guinea pig myometrium and heart. The HK and AK enzyme systems exhibited significant activity in isolated guinea pig uterine mitochodria in response to respiratory activity. The two enzyme systems were utilized by the uterine mitochondria to regulate the level of mitochondrial ADP and supplement the creatine kinase enzyme system in the maintenance of high-energy phosphate levels.