MITOCHONDRIAL HEXOKINASE OF AVOCADO MESOCARP

A hexokinase (EC 2.7.1.1) associated with the mitochondria of avocado (Persea americana) mesocarp has been characterized. The enzyme, which displayed typical hyperbolic kinetics, had substrate preference for glucose over fructose and mannose, and utilized MgATP most effectively as the phosphoryl donor. In experiments with intact mitochondria, hexokinase was susceptible to inactivation by proteolysis, indicating that it was located on the outer surface of the outer membrane. Aluminium ions were potent inhibitors at pH 6.8, with a concentration of ca 12 muM inhibiting glucose phosphorylation by 50%. Aluminium also inhibited the uptake of oxygen by mitochondria in the presence of glucose and ATP.