Nuclear location of phosphoglycerate mutase BB isozyme in rat tissues.

We have previously reported (Ure?a et al. Eur. J. Cell Biol. 1990) that in skeletal muscle, type MM phosphoglycerate mutase isozyme is present in the nucleus as well as in the cytosol. To determine whether type BB phosphoglycerate mutase isozyme is also present in nucleus, the subcellular location of this isozyme was studied in different rat tissues by cell fractionation and immunogold techniques. With the aid of high affinity-purified anti-phosphoglycerate mutase BB isozyme antibodies, the isozyme was located in the nucleus of neuronal, astroglial and liver cells but not in the nucleus of oligodendroglial and endothelial cells. Biochemical studies on purified nuclear fractions also demonstrated the presence of phosphoglycerate mutase activity in the nucleus. Both immunocytochemical and biochemical techniques showed that nuclear phosphoglycerate mutase-specific activity depended on the type of cell.     

Location of phosphoglycerate mutase in rat skeletal muscle. An immunocytochemical and biochemical study

The subcellular distribution of phosphoglycerate mutase was studied by immunogold techniques. With the aid of highly affinity-purified anti-phosphoglycerate mutase antibodies, the enzyme was found in both cytosol and nucleus of rat skeletal muscle. No evidence of interaction with contractile proteins was observed in cytosol. Nuclear location was also confirmed biochemically using purified nuclear preparations from rat skeletal muscle. Only one immunoreactive nuclear band was observed by Western blot experiments and corresponded to that of phosphoglycerate mutase mobility. Activity measurements from nuclear extracts showed that 25% of total specific activity is found in the nuclei.     

Metabolism of glycerate-2,3-P2--VII. Enzymes involved in the metabolism of glycerate-2,3-P2 in cat tissues

The levels of the enzymes involved in the metabolism of glycerate-2,3-P2 (phosphoglycerate mutase, bisphosphoglycerate synthase-phosphatase and bisphosphoglycerate phosphatase) in cat and in pig tissues are different. The main difference is the low level of bisphosphoglycerate synthase-phosphatase in cat tissues. As a consequence, in contrast with pig erythrocytes, in cat erythrocytes, both the synthesis and the breakdown of glycerate-2,3-P2 are mainly controlled by phosphoglycerate mutase.     

Isolation and sequencing of a cDNA encoding the B isozyme of rat phosphoglycerate mutase.

Phosphoglycerate mutase consists of two kinds of different subunits, M and B. We previously sequenced a rat cDNA encoding the type-M subunit. Here, we report the sequence of the type-B subunit-encoding cDNA. This cDNA has 1754 bp and contains a long 3'-untranslated region of 897 bp.     

Metabolism of glucose 1,6-P2--II. Glucose 1,6-P2 phosphatase in pig muscle

Most of the glucose 1,6-P2 phosphatase activity of pig skeletal muscle is present in the cytosolic fraction. Four peaks of glucose 1,6-P2 phosphatase activity are obtained when the cytosolic fraction from pig muscle is subjected to DE-cellulose chromatography. All the peaks hydrolyze other phosphocompounds in addition to glucose 1,6-P2. The glucose 1,6-P2 phosphatase activity of the main peak shows an optimal neutral pH. It is activated by divalent cations, Mg2+ being more effective than Mn2+. The addition of Ca2+ or EGTA does not affect the enzymatic activity. IMP does not possess any effect. It is concluded that this enzyme is different from the glucose 1,6-P2 phosphatases found in mouse brain cytosol and rat skeletal muscle.