Acid phosphatases bind to the main high density lipoprotein apolipoprotein A-I.

The serum protein binding secretory prostatic acid phosphatase (PAP) and lysosomal placental acid phosphatase (LAP) was purified using affinity chromatography on gels containing immobilized acid phosphatases. The protein, which could be eluted from these enzyme affinity gels only with 0.05 mol/l HCl (pH 2.0), was shown to be apolipoprotein A-I (apo A-I), the main structural protein of high density lipoprotein (HDL).