Rabbit Lactic Dehydrogenase and Rabbit Adenylate Kinase Inhibitions by Ascorbate and Ascorbate Fatty Derivatives and the Effects Spinach and Rabbit Muscle Aldolases

Previous studies showed that ascorbate specifically inhibited enzymes associated with promotion of rabbit muscle glycolysis – adenylate kinase (AK), lactate dehydrogenase (LDH), and phosphofructokinase-1 (PFK-1). It was proposed that these inhibitions facilitated glycogen synthesis by preventing degradation of glucose 6-phosphate, a precursor for both glycogen synthesis and degradation to pyruvate. A hypothesis was developed that ascorbate inhibits glycolysis to facilitate glucose 6-phosphate synthesis to glycogen in resting muscle. When muscle is active, contractile proteins form a complex with glycolytic enzymes that protects them from ascorbate inhibition; glycogen breaks down to form glucose 6-phosphate; glycolysis proceeds to generate ATP; and muscle contracts. Our studies revealed that rabbit muscle aldolase protected AK, LDH, and PFK-1 from inhibitions by ascorbate; these protections are viewed as a microcosm of in situ complex formations with contractile proteins. We show that spinach aldolase is also an efficient protector of AK, LDH, and PFK-1 from inhibitions by ascorbate. Similar to rabbit muscle aldolase, spinach aldolase also provides protection from inhibitions by ascorbic acid derivatives. Cross species interactions of spinach aldolase with AK, LDH, and PFK-1 from rabbit muscle suggest an evoluntionary conservative relationship between these enzymes.