Immunological and structural relatedness of isozymes and genetic variants of 3-phosphoglycerate kinase from the mouse.

Isozymes (PGK-1 and PGK-2) and genetic variants (PGK-2A, PGK-2B, and PGK-2C) of 3-phosphoglycerate kinase were purified by affinity chromatography using an 8-(6-aminohexyl)-amino-ATP-Sepharose column as the key step. Antisera raised against purified PGK-1 and PGK-2A were tested for specificity and cross-reactivity by application of double immunodiffusion and enzyme immunoinactivation methods. By double immunodiffusion, no precipitin lines were observed between anti-PGK-2A and PGK-1, but a weak cross-reactivity between anti-PGK-1 and PGK-2A was detected. In addition to specific inhibition of PGK-1 and PGK-2A by their respective antisera, anti-PGK-1 was shown to inhibit PGK-2 activity at high antiserum concentrations, whereas no inhibition of PGK-1 activity by anti-PGK-2A was observed. The amino acid compositions of PGK-1 and PGK-2 revealed a certain degree of homology. However, tryptic peptide maps showed no obvious similarity in the peptide spots between these two 3-phosphoglycerate kinase isozymes. Three electrophoretic variants of PGK-2 were compared biochemically and immunologically. PGK-2C from C57L/J mice, a low activity variant, was shown to be the result of a structural gene mutation that affects the active site of the enzyme.