Genetic variation of phosphoglucose isomerase in some hystricomorph rodents

Phosphoglucose isomerase electrophoretic variation has been studied in hystricomorph rodents. Intraspecies variation was found in chinchilla (Chinchilla laniger) and cuis (Galea musteloides). Interspecies hybridization of Cavia aperea and Cavia porcellus was found to produce hybrid enzymes. In all cases, breeding data indicated an autosomal mode of inheritance, while electrophoretic patterns were consistent with a dimeric structure for the enzyme. Possible evolutionary relationships of phosphoglucose isomerase with respect to taxonomy are discussed.The laboratory studies were supported by the Royal Society and Agricultural Research Council (N. D. C. and M. R. H.) and the Ford Foundation (B. J. W.).     

Biochemical and immunological characterization of genetic variants of phosphoglucose isomerase from mouse

Two electrophoretic variants of phosphoglucose isomerase (PGI) were purified from whole body extracts of DBA/2J and C57BL/6J mice by a substrate-affinity elution from an 8-(6-aminohexyl) amino-ATP-Sepharose column followed by preparative isoelectric focusing. Both PGI variants were shown to be dimers of the same molecular weight, sedimentation coefficient, and K _m for fructose-6-phosphate. The isoelectric points were found to be 8.4 and 8.7 for variants from DBA/2J and C57BL/6J mice, respectively. Differential thermal stability was observed for the two variants in 0.1 m tris-HCl buffer, pH 8.0, at 54 C; the half-lives of the purified PGI from DBA/2J and C57BL/6J mice were shown to be 3.4 and 1.8 min, respectively, under those conditions. Similar differences were observed for the enzyme variants in the crude homogenates. Antisera against PGI from DBA/2J mice were raised in rabbits. The variants from DBA/2J and C57BL/6J mice showed no significant differences in their respective inactivation curves by the antisera. Results of amino acid composition analyses and peptide mappings of the two PGI variants indicate that the genetic variation of this enzyme might result from a single charged amino acid substitution.D. J. C. is a National Institutes of Health Visiting Fellow.     

Evidence against the occurrence of tissue-specific variants and isoenzymes of phosphoglucose isomerase

Phosphoglucose isomerase (EC 5.3.1.9) from a variety of rat and human tissues has been studied by several electrophoretic techniques. When heart, liver, kidney, brain, erythrocyte, or skeletal muscle extracts were subjected to electrophoresis on cellulose acetate, a broad electrophoretic band was observed. When tissues were subjected to isoelectric focusing in sucrose density gradients or polyacrylamide gels, multiple peaks were observed unless the extracts were prepared and focused in the presence of reducing agents. In the presence of 2-mercaptoethanol or dithiothreitol phosphoglucose isomerase from different tissues co-focused as a single peak (apparent isoelectric pH = 9.23 for human and 8.40 for rat), suggesting that the enzyme from the various tissues is identical, and that tissue-specific variants do not exist. The electrophoretic multiplicity previously reported by other investigators may be due to artifacts arising from oxidation of the enzyme.     

Biochemical characterization of phosphoglucose isomerase and genetic variants from mouse and Drosophila melanogaster

Summary A simple and unique procedure was developed to purify phosphoglucose isomerase variants from the whole mouse body extracts and Drosophila homogenate. It involved the use of an 8-(6-aminohexyl)-amino-ATP-Sepharose column followed by a preparative isoelectric focusing. In each case, the enzyme in the homogenate was adsorbed by ionic interaction on the ATP-Sepharose column. Substantial purification was achieved by the affinity elution with the substrate-glucose-6-phosphate. Mouse and Drosophila phosphoglucose isomerase as well as the corresponding variants were shown to be dimers of similar molecular weight and to exhibit similar kinetic properties. The isoelectric points for the variants from DBA/2J and C57BL/6J mice were determined to be 8.4 and 8.7 respectively, while they were 6.8 and 6.3 respectively for Drosophila and 4/4 variants. Differential thermal stability was observed for the two mouse variants but not for the Drosophila ones. Amino acid composition analysis was performed for both mouse and Drosophila enzymes. Rabbit antisera for mouse (DBA/2J) and Drosophila (2/2) enzymes were raised. Within each species, complete immunological identity was observed between the variants. The antisera were used to characterize the null mutants of phosphoglucose isomerase identified in the mouse and Drosophila populations. By rocket immunoelectrophoresis, the null allele of the naturally occurring heterozygous null variant of Drosophila was shown to express no cross-reacting materials (CRM).     

Duplicated phosphoglucose isomerase genes in avocado

Summary Avocado (Persea americana) cultivars were assayed for phosphoglucose isomerase (PGI) isozymes using starch gel electrophoresis. Three PGI genes were identified: one monomorphic locus, Pgi-I, coding for the plastid isozyme and two independently assorting loci, Pgi-2 and Pgi-3, coding for the cytosolic isozymes. The genetic analysis was based on comparisons of PGI zymograms from somatic and pollen tissue and on Mendelian analysis of progeny from selfed trees. The isozymic variability for PGI can be used for cultivar identification and for differentiating between hybrid and selfed progeny in avocado breeding.     

The histochemical demonstration of phosphoglucose isomerase

Summary A technique for the histochemical demonstration of phosphoglucose isomerase, using an indirect tetrazolium method, is described. The enzyme is shown to be widely distributed, thus confirming biochemical findings. The wide distribution is of significance because phosphoglucose isomerase occupies a position of considerable importance in carbohydrate metabolism, particularly in the conversion of fructose to glucose by means of intermediate phosphates.     

A variant of rabbit phosphoglucose isomerase

An autosomally inherited variant of the rabbit enzyme phosphoglucose isomerase that differs both electrophoretically and kinetically from the usual (wild-type) rabbit enzyme has been investigated. Animals homozygous for this character have an isomerase with considerably decreased activity (in the erythrocytes), an increased K(m) for fructose 6-phosphate, an increased K(i) for 6-phosphogluconate and a decreased stability towards heat and urea. The variant enzyme has been demonstrated in erythrocytes, leucocytes and tissues from the affected rabbits. The kinetic evidence suggests that the mutation present in the variant enzyme affects a histidine residue.     

Two human red cell phosphohexose isomerase variants in a sample from the population of Rome

Summary In a population sample of 333 unrelated individuals from Rome 2 variants, PHI 3-1 and PHI 5-1, were found.

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Zusammenfassung Bei Untersuchungen einer Bevölkerungsgruppe von 333 nicht miteinander verwandten Personen aus Rom wurden 2 Varianten, PHI 3-1 und PHI 5-1, gefunden.

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This investigation was supported by a Grant of the Consiglio Nazionale delle Ricerche (CNR).     

Phosphoglucose isomerase and phosphoglucose mutase isozymes in some freshwater fishes from Basrah,Iraq

Two phosphoglucose isomerases and one phosphoglucose mutase with different specificities have been found in all groups of teleostean fishes studied. PGI and PGM proved to be good taxonomic criteria to differentiate members of the families Cyprinidae and Mugilidae from the other teleost families.     

Molecular characterization of pig muscle phosphoglucose isomerase

As a corollary to X-ray crystallographic work performed by H. Muirhead, detailed studies on crystalline pig muscle phosphoglucose isomerase have been conducted to establish its basic physical and chemical properties. The enzyme species being investigated by X-ray diffraction has been determined to be isoenzyme III. Its molecular weight in the native state was found to be 132,000, its s⁰₂₀,w value to be 7·25 S. The enzyme is composed of two subunits of equal molecular weight (66,000). Its amino acid composition is largely similar to that of rabbit muscle phosphoglucose isomerase, with the significant exception that the pig muscle isomerase contains only three sulfhydryl groups per polypeptide chain (two of them accessible to titration with p-mercuribenzoate) as compared with twice that number for the rabbit muscle enzyme. This low number of sulfhydryl groups is interpreted as being responsible for the ease with which heavy-atom, isomorphous derivatives could be prepared for the pig muscle enzyme by Shaw & Muirhead (1977).