title: Homodimer and heterodimer subunits of human prostate acid phosphatase.
abstract: Human prostatic acid phosphatase (PAP) isoenzymes, designated PAP-A and PAP-B, were isolated from human seminal plasma by sequential affinity chromatography on concanavalin A and L(+)-tartrate, a classic inhibitor of PAP. Both the major PAP-A and the minor PAP-B isoenzymes exhibited a similar molecular mass (100 and 105 kDa respectively), multiple pI values (5.05-5.35 and 5.05-5.12), and substrate and inhibitor specificity. Immunological characterization revealed that PAP-B possesses distinct antigenic determinants, in addition to the common sites shared with PAP-A. SDS/PAGE indicated that both isoenzymes are composed of two subunits of 50 kDa each. At high salt concentration, PAP-B dissociated completely into single subunits of 50 kDa, whereas PAP-A remained intact at 100 kDa. PAP-B was resolved by reverse-phase h.p.l.c. into three components, designated alpha, beta and gamma, each of 50 kDa, at a molar ratio of approx. 2:1:1. PAP-A contained a single component of molecular mass 50 kDa. The single component of PAP-A and the alpha component of PAP-B possessed identical amino acid compositions and N-terminal sequences, which were different from those of the beta and gamma components. These results indicate that human PAP contains three isoforms, alpha 2, alpha beta and alpha gamma. PAP-A, the major isoenzyme, is a homodimer consisting of two identical subunits (alpha 2), and PAP-B, the minor isoenzyme, is a mixture of two heterodimers, consisting of non-identical subunits (alpha beta and alpha gamma).
authors.affiliation: Department of Diagnostic Immunology Research and Biochemistry, Roswell Park Memorial Institute, Buffalo, NY 14263.
authors.forename: H
authors.initials: H
authors.lastname: Lee
authors.forename: T M
authors.initials: TM
authors.lastname: Chu
authors.forename: S S
authors.initials: SS
authors.lastname: Li
authors.forename: C L
authors.initials: CL
authors.lastname: Lee
mesh_terms: D000135:Acid Phosphatase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification; D015153:Blotting, Western; D006801:Humans; D005779:Immunodiffusion; D007526:Isoelectric Point; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification; D007700:Kinetics; D046911:Macromolecular Substances; D008297:Male; D015394:Molecular Structure; D008970:Molecular Weight; D011467:Prostate / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D046911:Macromolecular Substances; D000135:Acid Phosphatase