Fig 8. Catalytic activity of PP2A following its demethylation by L-homocysteine and adenosine treatment.

Caudal sperm incubated with 1 mM L-homocysteine and adenosine were sonicated and the soluble protein fraction was collected. Protein phosphatase activity in this fraction was measured with phosphorylase a as the substrate. PP2A activity was measured as the activity that can be inhibited by 2nM OA. Demethylation of sperm PP2A by L-homocysteine and adenosine results in decreased total phosphatase and PP2A catalytic activity. The mean phosphatase activities from five sets of experiments are represented as mmol of PO4 released/minute/2x10⁵ sperm ± SEM. ‘*’ denotes significant difference with P< 0.05. The demethylation in each experiment was confirmed by western blot analysis of the sperm extract.