Developmental changes in the pyruvate kinase isozymes of coho salmon

Purification and properties of two isozymes of pyruvate kinase from Mucor racemosus

The dimorphic phycomycete Mucor racemosus was found to contain up to five electrophoretic forms of pyruvate kinase (ATP: pyruvate 2-O-phosphotransferase, EC 2.7.1.40) depending on growth conditions. M. racemosus hyphal cells grown on glutamic acid as the carbon source contained only the fastest electrophoretic form, designated PK1, while yeast cells grown on glucose contained only the slowest electrophoretic form, PK5. Intermediate electrophoretic forms PK2, PK3, and PK4 as well as PK1 and PK5 were found in hyphal cells grown on media containing fructose or cellibiose. All five electrophoretic forms had molecular weights of ca. 230,000 as determined from plots of log Rm versus acrylamide gel concentration. Both PK1 and PK5 were purified to homogeneity and determined to be homotetramers, with subunit molecular weights of 54,000 and 58,100, respectively. The amino acid content of PK1 and PK5 was determined and found to be similar but not identical. Analysis of limited tryptic digests and cyanogen bromide cleavage fragments of PK1 and PK5 indicate that the subunits of the two isozymes are significantly different.

Liver specific pyruvate kinase in pheasants Phasianus colchicus

While in chickens, the existence of a liver form of pyruvate kinase is controversial, the liver form of pyruvate kinase in pheasants, murres and puffins is electrophoretically distinct from that in muscle, brain, kidney, lung and small intestine. Although the forms in lungs, muscle, heart, brain and small intestine could not be reliably separated by electrophoresis, the functional characteristics of the lung and muscle forms of pyruvate kinase in the pheasant are distinct and can be classified as K and M isozymes respectively. Our data suggest that these birds possess at least three distinct isozymes of pyruvate kinase.

Evolution of the functional properties of pyruvate kinase isozymes: pyruvate kinase L from Rana pipiens

The regulatory properties of type L pyruvate kinase from Rana pipiens are intermediate between those of the mammalian K and L isozymes. As with mammalian type L, the levels of the frog isozyme are affected by the animal's nutritional state. The mammalian and amphibian isozymes show similar sensitivities to fructose 1,6-bisphosphate activation and amino acid inhibition. By contrast, the frog L isozyme shares several properties of the K class: i.e. irreversible inactivation by oxidized glutathione and lack of response to a cyclic AMP stimulated phosphorylation. Furthermore, as for some mammalian K isozymes, frog type L shows a high PEP affinity and a low cooperativity of PEP binding. Insofar as the properties of this present day enzyme reflect those of its counterpart in the amphibian ancestor of higher vertebrates, our results suggest that at its first expression, the type L resembled the type K. Many important regulatory properties of the L isozyme, especially the sensitivity to phosphorylation, were acquired more recently perhaps in association with an increased importance of constant blood glucose.

Peptide structures of pyruvate kinase isozymes: 2. Origins of types M1 and M2 isozymes suggested from species-variations in their peptide maps

Pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) isozymes were purified: type M1 and M2 isozymes from rat, mouse and rabbit, type M1 from bull frog and type L from rat and mouse. The amino acid composition of type M1 and M2 isozymes from various species were very similar and those of type L isozymes from rat and mouse also very similar. The NH2-terminals to type M1 and M2 from rat and mouse were (Pro-Lys-Pro-), but those of the other enzymes appeared to be blocked. The COOH-terminals of type M1 and M2 from rat, mouse and rabbit were (-Val-Pro). Comparison of tryptic peptide maps of type M1 and M2 from rat, mouse and rabbit indicated that type M1 and M2 could not be produced by post-synthesis modification, but could be encoded by different type-specific mRNAs. Comparative studies on type M1 and M2 of different species showed that type M1-specific peptide spots were highly variable, whereas type M2-specific peptide spots were highly conserved. The type L isozyme showed marked species variation, indicating that this differentiated isozyme evolved more rapidly than type M2, which may be a prototype or undifferentiated isozyme.

Pyruvate kinases of salmon: purification and comparison with the isozymes from birds and mammals

Pyruvate kinase occurs as two major forms in coho salmon; the type M isozyme occurs primarily in muscle and heart, but type K has a more generalized tissue distribution, in parallel with the type K isozyme in other vertebrate systems. In order to assess the evolutionary relationships among the fish, avian, and mammalian isozymes of pyruvate kinase, we have purified the two isozymes from fish, have examined some of their physical properties, and have studied their immunological relationships to the avian and mammalian isozymes. Salmon type K is at least partially inactivated by antibody to bivine type L pyruvate kinase as well as by antibodies produced against chicken, bovine, and salmon type M isozymes. Salmon type M pyruvate kinase, on the other hand, is not significantly corss-reactive with the bovine type L isozyme, but is at least partially inactivated by antibodies produced against bovine or chicken type M isozymes. Mammalian type L pyruvate kinase is immunologically distinct from either mammalian type K or type M, but salmon type K has some structural features in common with all three mammalian isozymes. Thus, salmon fish type K pyruvate kinase could be similar to a primordial form that was antecedent to the three major differentiated isozymes of higher vertebrates.