The association of distinct acid phosphatases with the flagella pocket and surface membrane fractions obtained from bloodstream forms of Trypanosoma rhodesiense.

Cell fractionation of bloodstream Trypanosoma rhodesiense, using isopycnic sucrose gradient centrifugation, reveals acid phosphatase activities against a range of substrates to be associated, to varying degrees, with subcellular particle populations identified as derived from flagella pocket membrane and surface membrane. Using these same substrates (alpha and beta glycerophosphate, p-nitrophenyl phosphate and glucose-6-phosphate) at least two distinct acid phosphatase activities can be distinguished. One is thermolabile (approximately 80% inactivated after 30 min. at 60 degrees C), sensitive to tartrate (50% inhibited at 1.8 mM Na tartrate) with a pH optimum approximately 4.5 and appears to exhibit little substrate preference. The other acid phosphatase is relatively heat stable (approximately 30% inactivated), insensitive to tartrate (greater than 5.0% inhibited using 1.8 mM Na tartrate) exhibits a somewhat higher pH optimum (approximately 6.0) and is more substrate specific (6X more active toward glucose-6-PO4 than beta-glycerophosphate). Further cell fractionation experiments reveal 85% of the tartrate sensitive acid phosphatase to be associated with flagella pocket membrane and to account for 80% of the organisms hydrolytic activity toward beta-glycerophosphate. The tartrate resistant acid phosphatase however, has a much less exclusive localization being almost equally distributed between surface membrane (40%) and flagella pocket membrane (60%).