Binding sites of seminal acid phosphatase to Canavalia gladiata DC lectin

Binding sites of seminal acid phosphatase (AcP) to Canavalia gladiata DC lectin (Can G) were examined. Complex of AcP and Can G produced in a test tube was solubilized with alpha-methyl-D-mannoside and was fractionated with Sephadex G-200. The elution pattern of AcP activity of the complex was similar to that of seminal plasma, suggesting that the reaction of AcP and Can G was reversible. Crossed immuno-affinoelectrophoresis with intermediate gel containing free Can G or immobilized one showed that AcP molecule had two or more binding sites per molecule to Can G. AcP activity of frozen sections of the prostate was inhibited by tartaric acid but not by Can G. However, Can G bound to AcP of the sections could be detected with FITC-labeled anti-Can G. These results indicate that the active site of AcP to Can G is not identical with that to the substrate.