Phosphatase activity in the ocular tissues.

This specific phosphatase is a 5-nucleotidase; it differs from the alkaline phosphatase in its range of action and in its optimal pH. Whereas alkaline phosphatase, which is non-specific, hydrolyses a great variety of phosphoric esters, the 5-nucleotidase hydrolyses only nucleotides with the phosphate group attached to the fifth carbon of the pentose, that is, muscle adenylic acid (adenosine-5-monophosphoric acid) and inosinic acid (inosine-5-monophosphoric acid). The optimal pH of alkaline phosphatase is near pH 9.5; the optimal pH of 5-nucleotidase is at pH 7.8 (for human tissues), which approaches the physiological hydrogen ion concentration.