Direct promotion of collagen calcification by alkaline phosphatase

Alkaline phosphatase promotes hydrolysis of phosphate containing substrates causes a rise in inorganic phosphate and therefore enhances calcification of biological tissues. In this work the calcification of collagen in a model serum was used as a model of collagenous tissue biomaterials to study the possible calcification promotion mechanism of alkaline phosphatase. In the enzyme concentration range of 0.1–0.5 mg/mL the enzyme shows a direct calcification promoting effect which is independent of the hydrolysis of its phosphate containing substrates but proportional to the enzyme concentration. Potassium pyrophosphate somewhat inhibits the calcification promotion.