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PubMed1997

[Effects of genetic polymorphism of phosphoglucomutase identifiable in human milk (PGM4 locus) on the somatotype of the newborn and reproductive function of women].

The polyacrylamide gel isoelectrofocusing technique was used to examine structural variations of the human milk-expressed enzyme PGM4-locus phosphoglucomutase. Six phenotypes controlled by four alleles: PGM4*1, PGM4*2, PGM4*3, PGM4*4 with frequencies of 0.261, 0.664, 0.047, 0.028, respectively, were identified in 180 milk samples taken from Moscow Russian women in labour. The empirical distribution of the PGM4 phenotypes is in a moderate agreement with the expected one with chi 2 = 9.622; 6 d.f. (p > 0.05). Its phenotypic belonging to PGM4 1-2 and PGM4 2-2 was examined for its influence on female reproductive function and neonatal somatic type. The PGM4 1-2 phenotype was positively associated with miscarriages whereas PGM4 2-2 negatively correlated with this abnormality. If the mother had PGM4 2-2, there might be increased body dimensions (body length and mass, head and chest circumferences) in male neonates. On the contrary, PGM4 1-2 was negatively correlated with body length and mass in the newborns of both sexes. For female neonates, there was a highly significant association only with the presence of PGM4 2-2 in their mothers, namely: its presence was positively correlated with all body dimensions.

Chromosome Mapping↗
PubMed1976

[Investigation of electrophoretical enzyme phänotypes glucose-6-phosphate dehydrogenase, red cell acid phosphatase, phosphoglucomutase and adenosine deaminase of permanent human cell lines (author's transl)].

Isoenzymes of 11 cell lines were investigated by electrophoretical separation. All lines have been cultivated from tissues of white persons, all but one (Leuc. Th. B.) were phosphoglucomutase 1 and all were adenosine deaminase 1. Three out of 11 cell lines did show glucose-6-phosphate dehydrogenase (G6PD) type B as expected. Two out of 8 cell lines with G6PD A were distinguishable by their specific type of "red cell" acid phosphatase (SEP). We conclude that in vitro the electrophoretical G6PD phänotyp B changed to phänotype A. Further 4 lines had other peculiarities which are indicative to their originality, though they were G6PD A. Our investigations did show that G6PD may become type A if a cell line changes to permanent growth capacity in vitro. The enzyme marker G6PD A alone may not be valuated as an absolute evidence for contamination or mix up with He-La Cells.

Acid Phosphatase↗
PubMed1976

[Mechanism of the phosphoglucomutase reaction].

The points of bonds ruptures in the course of phosphoglucomutase reaction were studied by two methods: incorporation of 18O and kinetic isotope effect with the use of double label (14C and 3H). The method of 18O determination by means of activation analysis is described. Analysis of data leads to the conclusion that phosphoryl, but not phosphate group, moves in the course of the reaction. Possible mechanisms of phosphoglutcomutase reaction are discussed.

Catalysis↗
PubMed2006

Conformational cycling in beta-phosphoglucomutase catalysis: reorientation of the beta-D-glucose 1,6-(Bis)phosphate intermediate.

Activated Lactococcus lactis beta-phosphoglucomutase (betaPGM) catalyzes the conversion of beta-d-glucose 1-phosphate (betaG1P) derived from maltose to beta-d-glucose 6-phosphate (G6P). Activation requires Mg(2+) binding and phosphorylation of the active site residue Asp8. Initial velocity techniques were used to define the steady-state kinetic constants k(cat) = 177 +/- 9 s(-)(1), K(m) = 49 +/- 4 microM for the substrate betaG1P and K(m) = 6.5 +/- 0.7 microM for the activator beta-d-glucose 1,6-bisphosphate (betaG1,6bisP). The observed transient accumulation of [(14)C]betaG1,6bisP (12% at approximately 0.1 s) in the single turnover reaction carried out with excess betaPGM (40 microM) and limiting [(14)C]betaG1P (5 microM) and betaG1,6bisP (5 microM) supported the role of betaG1,6bisP as a reaction intermediate in the conversion of the betaG1P to G6P. Single turnover reactions of [(14)C]betaG1,6bisP with excess betaPGM were carried out to demonstrate that phosphoryl transfer rather than ligand binding is rate-limiting and to show that the betaG1,6bisP binds to the active site in two different orientations (one positioning the C(1)phosphoryl group for reaction with Asp8, and the other orientation positioning the C(6)phosphoryl group for reaction with Asp8) with roughly the same efficiency. Single turnover reactions carried out with betaPGM, [(14)C]betaG1P, and unlabeled betaG1,6bisP demonstrated complete exchange of label to the betaG1,6bisP during the catalytic cycle. Thus, the reorientation of the betaG1,6bisP intermediate that is required to complete the catalytic cycle occurs by diffusion into solvent followed by binding in the opposite orientation. Published X-ray structures of betaG1P suggest that the reorientation and phosphoryl transfer from betaG1,6bisP occur by conformational cycling of the enzyme between the active site open and closed forms via cap domain movement. Last, the equilibrium ratio of betaG1,6bisP to betaG1P plus G6P was examined to evidence a significant stabilization of betaPGM aspartyl phosphate.

Amino Acid Sequence↗
PubMed1985

Alterations in Growth, Photosynthesis, and Respiration in a Starchless Mutant of Arabidopsis thaliana (L.) Deficient in Chloroplast Phosphoglucomutase Activity.

A mutant of Arabidopsis thaliana (L.) Heynh. which lacks leaf starch was isolated by screening for plants which did not stain with iodine. The starchless phenotype, confirmed by quantitative enzymic analysis, is caused by a single recessive nuclear mutation which results in a deficiency of the chloroplast isozyme of phosphoglucomutase. When grown in a 12-h photoperiod, leaves of the wild-type accumulated substantial amounts of starch but lower levels of soluble sugars. Under these conditions, the mutant accumulated relatively high levels of soluble sugars. Rates of growth and net photosynthesis of the mutant and wild-type were indistinguishable when the plants were grown in constant illumination. However, in a short photoperiod, the growth of the mutant was severely impaired, the rate of photosynthesis was depressed relative to the wild-type, and the rate of dark respiration, which was high following the onset of darkness, exhibited an uncharacteristic decay throughout the dark period. The altered control of respiration by the mutant, which may be related to the relatively high levels of soluble carbohydrate that accumulate in the leaf and stem tissue, is believed to be partially responsible for the low growth rate of the mutant in short days. The depressed photosynthetic capacity of the mutant may also reflect a metabolic adaptation to the accumulation of high levels of soluble carbohydrate which mimics the effects of alterations in source/sink ratio. The activities of sucrose phosphate synthase and acid invertase are significantly higher in the mutant than in the wild-type whereas ADP-glucose pyrophosphorylase activity is lower. This suggests that the activities of these enzymes may be modulated in response to metabolite concentrations or flux through the pathways.

Journal Article↗
PubMed1988

A Starchless Mutant of Nicotiana sylvestris Containing a Modified Plastid Phosphoglucomutase.

A mutant (NS 458) of Nicotiana sylvestris (Spegazzini and Comes) unable to synthesize leaf starch was isolated in the M(2) generation following ethyl methanesulfonate mutagenesis by testing with iodine. Segregation ratios in reciprocal F(2) progenies showed that the starchless phenotype resulted from a recessive mutation in a single nuclear gene. DEAE-agarose chromatography showed that the mutant is grossly deficient in plastid phosphoglucomutase (EC 2.1.5.1) activity. The structure of the enzyme is changed, as evidenced by increased Michaelis constants and by the prolonged activation period (>40 minutes) observed when the enzyme is assayed in triethanolamine buffer rather than imidazole buffer. The activity of the wild-type enzyme with saturating glucose 6-P alone was 7% of the activity when saturating glucose 1,6-P(2) was also present. The results suggest that glucose 1,6-P(2) is both an effector and a dissociable reaction intermediate. The growth rate of mutant and wild-type plants were not significantly different in continuous light and on an 8-hour dark, 16-hour light cycle and the mutants grew normally under greenhouse conditions. The mutant supports growth during diurnal periods of darkness by vacuolar storage of sugars instead of chloroplast storage of starch. The simplification in metabolism achieved by blocking the diversion of plastid fructose-6-P to starch facilitates the induction of oscillations in CO(2) fixation.

Journal Article↗
PubMed1989

Evidence for a light dependent increase of phosphoglucomutase activity in isolated, intact spinach chloroplasts.

Phosphoglucomutase (PGM) activity was measured in spinach (Spinacia oleracea L.) chloroplasts. Initial enzyme activity in a chloroplast lysate was 5 to 10% of total activity measured with 1 micromolar glucose 1,6-bisphosphate (Glc 1,6-P(2)) in the assay. Initial PGM activity increased 2- to 3-fold when chloroplasts were illuminated for 10 minutes prior to enzyme measurement and then decreased slowly in the dark. Measurements of total enzyme activity were unchanged by prior light treatment. Initial PGM activity from light treated chloroplasts was sufficient to account for in vivo rates of starch synthesis. Changes in PGM activity were affected by stromal pH and orthophosphate concentration. Photosynthetic inhibitors, dl-glyceraldehyde, glycolaldehyde, and glyoxylate, decreased and 3-phosphoglyceric acid increased light induced changes of PGM activity. Dark preincubation of chloroplasts with 10 millimolar dithiothreitol had no effect upon initial PGM activity, suggesting that light effects did not involve a sulfhydryl mechanism. Hexose monophosphate levels increased in illuminated chloroplasts. Activation of PGM in a chloroplast lysate by Glc 1,6-P(2) was maximal between pH 7.5 and 8.5. Stromal concentrations of Glc 1,6-P(2) were between 20 and 30 micromolar for both light and dark incubated chloroplasts and these levels should saturate PGM activity. Light dependent alterations of enzyme activity may be due to changes of phosphorylated PGM levels in the stroma or are the result of changes in residual activity by the dephosphorylated form of the enzyme. The above results indicate that PGM activity in spinach chloroplasts may be regulated by light, stromal pH, and Glc 1,6-P(2) concentration.

Journal Article↗
PubMed1990

Many maize inbreds lack an endosperm cytosolic phosphoglucomutase.

Starch gel electrophoresis of extracts from developing maize (Zea mays L.) endosperms 22 days postpollination reveals only a single zone of phosphoglucomutase activity in the majority of the inbreds tested. The other inbreds had the expected two zones of activity. The activity that is present in all inbreds is the amyloplast isozyme while the absent form is a cytosolic enzyme. The lack of the cytosolic isozyme has no discernible phenotypic consequences.

Journal Article↗
PubMed1997

Structure of rabbit muscle phosphoglucomutase refined at 2.4 A resolution.

Data between 6.0 and 2.4 A resolution, collected at 253 K, wer used to refine a revised atomic model of muscle phosphoglucomutase: final crystallographic R factor = 16.3% (Rfree = 19.1%); final r.m.s. deviations from ideal bond lengths and angles = 0.018 A and 3.2 degrees, respectively. Features of the protein that were recognized only in the revised model include: the disposition of water molecules within domain-domain interfaces; two ion pairs buried in domain-domain interfaces, one of which is a structural arginine around which the active-site phosphoserine loop is wound; the basic architecture of the active-site 'crevice', which is a groove in a 1(1/3)-turn helix, open at both ends, that is produced by the interfacing of the four domains; the distorted hexacoordinate ligand sphere of the active-site Mg2+, where the enzymic phosphate group acts as a bidentate ligand; a pair of arginine residues in domain IV that form part of the enzymic phosphate-binding site (distal subsite) whose disposition in the two monomers of the asymmetric unit is affected unequally by distant crystallographic contacts; structural differences throughout domain IV, produced by these differing contacts, that may mimic solution differences induced by substrate binding; large differences in individually refined Debye-Waller thermal factors for corresponding main-chain atoms in monomers (1) and (2), suggesting a dynamic disorder within the crystal that may involve domain-size groups of residues; and a 'nucleophilic elbow' in the active site that resides in a topological environment differing from previous descriptions of this type of structure in other proteins.

Journal Article↗
PubMed1997

Enhanced diffractivity of phosphoglucomutase crystals. Use of an alternative cryocrystallographic procedure.

A continuous procedure for replacing the 2 M (NH(4))(2)SO(4) within crystals of rabbit muscle phosphoglucomutase by 55% polyethylene glycol 600 (PEG 600) is described. The success rate (absence of fracturing) approaches 100% in spite of the fragility of the crystals. The procedure is based on the use of a biphasic PEG/salt mixture in conjunction with a flow cell that allows several crystals to be treated at once. The holdup volume of the cell is small and its design minimizes concentration gradients. Cooling treated crystals to 253 K elicits a substantial increase in diffractivity that allows data collection to be extended from about 2.75 to about 2.35 A. However, neither the dimensions of the unit cell nor the structure of the asymmetric unit are significantly altered. Comparisons are made between data sets collected at 289 K using crystals in 2.2 M (NH(4))(2)SO(4) and at 253 K using crystals in 55% PEG 600. Models of the enzyme refined against one or the other data sets are also compared. These comparisons suggest that, at most, only a minor fraction of the increased diffractivity is caused by lowered atomic B values. The increased diffractivity also is not the result of a simple temperature effect since at high-salt concentration the same cooling protocol fails to significantly increase diffractivity. A decrease in mosaic spread is considered as a possible explanation for the increased diffractivity.

Journal Article↗
PubMed2000

Identification of the pgmG gene, encoding a bifunctional protein with phosphoglucomutase and phosphomannomutase activities, in the gellan gum-producing strain Sphingomonas paucimobilis ATCC 31461.

The pgmG gene of Sphingomonas paucimobilis ATCC 31461, the industrial gellan gum-producing strain, was cloned and sequenced. It encodes a 50,059-Da polypeptide that has phosphoglucomutase (PGM) and phosphomannomutase (PMM) activities and is 37 to 59% identical to other bifunctional proteins with PGM and PMM activities from gram-negative species, including Pseudomonas aeruginosa AlgC. Purified PgmG protein showed a marked preference for glucose-1-phosphate (G1P); the catalytic efficiency was about 50-fold higher for G1P than it was for mannose-1-phosphate (M1P). The estimated apparent K(m) values for G1P and M1P were high, 0.33 and 1.27 mM, respectively. The pgmG gene allowed the recovery of alginate biosynthetic ability in a P. aeruginosa mutant with a defective algC gene. This result indicates that PgmG protein can convert mannose-6-phosphate into M1P in the initial steps of alginate biosynthesis and, together with other results, suggests that PgmG may convert glucose-6-phosphate into G1P in the gellan pathway.

Amino Acid Sequence↗
PubMed1998

Purification and some catalytic properties of phosphoglucomutase from maize leaves

Phosphoglucomutase (EC 2.7.5.1, PGM) was purified to homogeneity from maize (Zea mays L.) leaves. The enzyme had specific activity 11. 7 U/mg protein and molecular mass (determined by gel-chromatography) of 133 +/- 4 kD. The molecular mass of PGM subunits determined by SDS-electrophoresis was 66 +/- 3 kD. The enzyme had Km for glucose-1-phosphate and glucose-1,6-diphosphate of 20.0 +/- 0.9 and 16.0 +/- 0.8 &mgr;M, respectively. Concentrations of glucose-1-phosphate and glucose-1,6-diphosphate above 3 and 0.4 mM, respectively, cause substrate inhibition. The enzyme activity was maximal at pH 8.0 and temperature 35 degreesC. Magnesium ions activate the enzyme and manganese ions inhibit it. 3-Phosphoglycerate is an uncompetitive inhibitor of the enzyme (Ki = 1.22 +/- 0.05 mM). Fructose-6-phosphate, 6-phosphogluconate, and ADP activate PGM, whereas ATP, UTP, and AMP inhibit the enzyme. Citrate was also a potent inhibitor, inhibitory effects of isocitrate and cis-aconitate being less pronounced.

Journal Article↗