Characterization of ACP1TIC-1, an electrophoretic variant of erythrocyte acid phosphatase restricted to the Ticuna Indians of central Amazonas.

A new variant of erythrocyte acid phosphatase, designated ACP1TIC-1, is characterized by a more cathodal electrophoretic mobility than any of the common polymorphic phenotypes, both in the presence and absence of tricarboxylic acids. Individuals of the ACP1TIC-1 phenotype have a level of enzyme activity (4.8 +/- 0.1 mumol/g hemoglobin per min) similar to individuals of the ACP1A phenotype, although no differences in Km values were observed or is the extent of phosphate inhibition different between the ACP1TIC-1 and the ACP1B variants. The thermostability of the enzyme is less than that observed for any of the common variants. The TIC-1 variant is activated by adenine and inhibited by folic acid to the same extent as the type-A enzyme, while the stimulation of the activity of the TIC-1 enzyme by hypoxanthine and the inhibition of it by uric acid is similar to that for the B enzyme. Thus, the TIC-1 variant has a unique combination of kinetic properties, seeming to be a hybrid of A-type and B-type characteristics.