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PubMed1977

Comparative studies of lactic acid dehydrogenases in lactic acid bacteria. I. Purification and kinetics of the allosteric L-lactic acid dehydrogenase from Lactobacillus casei ssp. casei and Lactobacillus curvatus.

The stability, pH-dependence and kinetic properties of the Mn2+ and FDP-activated NAD-dependent lactic acid dehydrogenases from Lactobacillus casei ssp. casei (ATCC 393) and L. curvatus (DSM 20010) were studied after the enzymes were purified to homogeneity by affinity chromatography. Both enzymes are virtually unidirectional, catalysing efficiency only the reduction of pyruvate. They are similar with respect to the effector requirement and pH-optimum. They differ, however, in their electrophoretic mobility, heat stability, pH-dependence of the Mn2+ requirement and several kinetic properties. It is suggested that most of these differences are caused by differences of the negative charges in the vicinity of the FDP-binding site or the site responsible for the interaction of the subunits of the enzymatically active oligomeres.

Allosteric Regulation↗
PubMed1977

Fructose metabolism in four Pseudomonas species.

1. ATP-Dependent phosphorylation of fructose could not be detected in extracts of fructose-grown cells of Pseudomonas extorquens strain 16, Pseudomonas 3A2, Pseudomonas acidovorans and Pseudomonas fluorescens. Instead, phosphorylation of fructose to fructose-1-phosphate was found to occur when cell-free extracts were incubated with fructose and phosphoenolpyruvate. Such an activity could not be detected in cell-free extracts of succinate-grown cells. 2. High levels of 1-phosphofructokinase were found in extracts of the above organisms when growth on fructose. 3. Mutants of Pseudomonas extorquens strain 16 lacking 1-phosphofructokinase were unable to grow on fructose. Revertants to growth on fructose had regained the capacity to synthesize this enzyme, indicating its necessary involvement in fructose metabolism. 4. A survey has been carried out of enzymes involved in carbohydrate metabolism in the species listed above.

Cell-Free System↗
PubMed1975

Catabolism of D-fructose and D-ribose by Pseudomonas doudoroffii. I. Physiological studies and mutant analysis.

Pseudomonas doudoroffii, a strict aerobe of marine origin, was able to utilize fructose and ribose but not glucose, gluconate, or other hexoses, pentoses, or sugar alcohols as sole sources of carbon and energy. Evidence was presented indicating that in this organism fructose was utilized via an inducible P-enolpyruvate: fructose phosphotransferase system (FPTS) which catalyzed the phosphorylation of fructose in the 1 position. The resulting fructose-1-P (F-1-P) was converted to fructose-1,6-P2 (FDP) by means of an inducible 1-P-fructokinase (1-PFK). The subsequent conversion of FDP to pyruvate involved enzymes of the Embden-Meyerhof pathway (EMP) which, with the exception of glyceraldehyde-3-P dehydrogenase (G3PDH), were constitutive. Two G3PDH activities were detected, one of which was inducible and NAD-dependent while the other was constitutive and NADP-dependent. Cell-free extracts of P. doudoroffii also contained enzymes of the methylglyoxal pathway (MGP) which converted dihydroxyacetone-P to pyruvate. The low specific activities of enzymes of this pathway as compared to the EMP suggested that the major route of FDP catabolism was via the latter pathway. 2. Ribose catabolism appeared to involve an inducible uptake system and an inducible ribokinase, the resulting ribose-5-P being converted to glyceraldehyde-3-P and fructose-6-P (F-6-P) by means of constitutive activities of the pentose-P pathway. The F-6-P formed as a result of these reactions was converted to FDP by means of a constitutive 6-P-fructokinase (6-PFK). Since no activity converting fructose or F-1-P to F-6-P could be detected in cell-free extracts of P. doudoroffii, the results suggested that fructose and ribose were catabolized via 1-PFK and 6-PFK, respectively, the two pathways converging at the level of FDP. Further evidence for this suggestion was obtained from a mutant which lacked an NAD-dependent G3PDH, accumulated FDP from both fructose and ribose, and was not able to grow on either of these compounds. 3. Ribose grown cells had increased amounts of the fructose uptake system and 1-PFK suggesting that a compound (or compounds) common to the catabolism of both fructose and ribose acted as the inducer(s) of these activities. Evidence was presented suggesting that the probable inducer(s) of 1-PFK and FPTS could be FDP, glyceraldehyde-3-P, or dihydroxyacetone-P. 4. A mutant unable to grow on fructose was characterized and found to lack FPTS while retaining 1-PFK and other enzyme activities of the EMP and MGP, indicating that a functional FPTS was essential for growth on fructose and suggesting that all or most of this sugar was catabolized via F-1-P.

Dihydroxyacetone Phosphate↗
PubMed1975

Catabolism of D-fructose and D-ribose by Pseudomonas doudoroffii. II. Properties of 1-phosphofructokinase and 6-phosphofructokinase.

1. The 1-P-fructokinase (1-PFK) and 6-P-fructokinase (6-PFK) from Pseudmonas doudoroffii were partially purified by a combination of (NH4)2SO4 fractionation and DEAE-Sephadex column chromatography. The pH optima of these enzymes were 9.0 and 8.5, respectively. 2. When the concentrations of the substrates of the 1-PFK reaction were varied, Michaelis-Menten kinetics were observed. The Kms for D-fructose-1-P (F-1-P) and ATP were 3.03 X 10(-4) M and 3.39 X 10(-4) M, respectively. Variation of MgCl2 at fixed concentrations of F-1-P and ATP resulted in sigmoidal kinetics; about 10 mM MgCl2 was necessary for maximal activity. Activity of 1-PFK was inhibited when the ratio of ATP:Mg++ was higher than 0.5, suggesting that ATP:2Mg++ was the substrate and that free ATP was inhibitory. Although an absolute requirement for K+ or NH4+ could not be demonstrated, these cations stimulated the rate of the reaction. Activity of 1-PFK was not significantly affected by 3 mM AMP, cyclic-AMP, Pi, D-fructose-6-P (F-6-P), ADP, P-enolpyruvate (PEP), pyruvate, citrate, or L-gluamate. 3. Sigmoidal kinetics were observed for 6-PFK when the concentration of F-6-P was increased and the level of ATP was kept constant. Activity of 6-PFK was increased by ADP, inhibited by PEP, and unaffected by 3 mM AMP, cyclic-AMP, Pi, F-1-P, pyruvate, or citrate.

Adenosine Triphosphate↗
PubMed1975

Purification and properties of a fructose-1,6-diphosphate activated L-lactate dehydrogenase from Staphylococcus epidermidis.

L-(+)-lactate dehydrogenase (LDH) from Staphylococcus epidermidis ATCC 14990 was purified by affinity chromatography. The purified enzyme was specifically activated by fructose-1,6-diphosphate (FDP). The concentration of FDP required for 50% maximal activity was about 0.15 mM. The enzyme activity was inhibited by adenosine diphosphate (ADP) and oxamate. The inhibition by ADP appeared to be competitive with respect to reduced nicotinamide adenine dinucleotide (NADH). The catalytic activity of the LDH for pyruvate reduction exhibited an optimum at pH 5.6. The enzyme is composed of four, probably identical, subunits. Sephadex gel filtration and sedimentation velocity at pH 5.6 Yielded molecular weights of about 130 000 and 126 000, respectively. The molecular weight at pH 6.5 and 7.0 was found to be only about 68 000. Polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate and sedimentation velocity at pH 2.0 or 8.5 revealed monomeric subunits with an approximate molecular weight of 36000. The thermostability of the heat labile enzyme was increased in the presence of FDP, NADH and pyruvate. The purified LDH exhibited an anomalous type of kinetic behavior. Plots of initial velocity vs. different concentrations of pyruvate, NADH or FDP led to saturation curves with intermediary plateau regions. As a consequence of these plateau regions the Hill coefficient alternated between lower and higher n-values. Some distinguishing properties of the S. epidermidis LDH and other LDHs activated by FDP are discussed.

Adenine Nucleotides↗
PubMed1976

Pyruvate kinase isozymes in man. II. L type and erythrocyte-type isozymes. Electrofocusing and immunologic studies.

By focusing in sucrose, gradient L-type pyruvate kinase from human liver could be separated into 2 major forms (pI 6.28 +/- 0.03 and 5.85 +/- 0.09) and a minor more acid form (pI = 5). These different forms could also be detected by focusing in acrylamide-ampholine slab gel. The major forms were interconvertible, the equilibrium being shifted toward the acid form by fructose 1,6-diphosphate and SH reagents, and toward the alkaline form by proteinic factors extracted by ammonium sulphate fractionation from liver extracts and from hemolysates. These factors seemed to be responsible for the stabilization of the liver crude extract enzyme in its alkaline conformation. By acrylamide slab gel electrofocusing, erythrocyte pyruvate kinase from whole hemolysates exhibited a complex pattern composed of at least 3 introconvertible forms. The in vitro aging of the red blood cells and the storage of the hemolysates resulted in a progressive disappearance of the acid forms and in a strengthening of the alkaline form. Partially purified erythrocyte enzyme focused in 2 major bands, interconvertible under the influence of the same factors as those described for L-type pyruvate kinase. Although closely related, the focusing patterns of L-type and erythrocyte-type were never exactly identical. Double immunodiffusion against antihuman erythrocyte-and L-type pyruvate kinases. Moreover, antihuman M2-type serum was unable to neutralize erythrocyte pyruvate kinase as well as to change its electrophoretic mobility. Consequently, we conclude that both human erythrocyte- and liver L-type pyruvate kinases existed under several conformers interconvertible under the influence of the same ligands or proteinic factors; erythrocyte-type enzyme seems to include L-type subunit and not M1- or M2-type subunits. The erythrocyte- and L-type enzymes, however, are not identical and the nature of the differences between them is discussed.

Cross Reactions↗
PubMed1981

Erythrocyte phosphofructokinase in rat strains with genetically determined differences in 2,3-diphosphoglycerate levels.

We have studied the erythrocyte enzyme phosphofructokinase (PFK) from two strains of Long-Evans rats with genetically determined differences in erythrocyte 2,3-diphosphoglycerate (DPG) levels. The DPG difference is due to two alleles at one locus. With one probable exception, the genotype at this locus is always associated with the hemoglobin (Hb) electrophoretic phenotype, due to a polymorphism at the III beta-globin locus. The enzyme PFK has been implicated in the DPG difference because glycolytic intermediate levels suggest that this enzyme has a higher in vivo activity in High-DPG strain rats, although the total PFK activity does not differ. We report here that partially purified erythrocyte PFK from Low-DPG strain cells is inhibited significantly more at physiological levels of DPG (P less than 0.01) than PFK from High-DPG strain erythrocytes. Citrate and adenosine triphosphate also inhibit the Low-DPG enzyme more than the High-DPG enzyme. Therefore, a structurally different PFK, with a greater sensitivity to inhibitors, may explain the lower DPG and ATP levels observed in Low-DPG strain animals. These data support a two-locus (Hb and PFK) hypothesis and provide a gene marker to study the underlying genetic and physiologic relationships of these loci.

Adenosine Triphosphate↗
PubMed1976

Quantitative cytochemical measurement of glyceraldehyde 3-phosphate dehydrogenase activity.

A system has been developed for the quantitative measurment of glyceraldehyde 3-phosphate dehydrogenase activity in tissue sections. An obstacle to the histochemical study of this enzyme has been the fact that the substrate, gylceraldehyde 3-phosphate, is very unstable. In the present system a stable compound, fructose 1, 6-diphosphate, is used as the primary substrate and the demonsatration of the glyceraldehyde 3-phosphate dehydrogenase activity depends on the conversion of this compound into the specific substrate by the aldolase present in the tissue. The characteristics of the dehydrogenase activity resulting from the addition of fructose 1, 6-diphosphate, resemble closely the known properties of purified glyceraldehyde 3-phosphate dehydrogenase. Use of polyvinyl alcohol in the reaction medium prevents release of enzymes from the sections, as occurs in aqueous media. Although in this study intrinsic aldolase activity was found to be adequate for the rapid conversion of fructose 1, 6-diphosphate into the specific substrate for the dehydrogenase, the use of exogenous aldolase may be of particular advantage in assessing the intergrity of the Embden-Meyerhof pathway.

Animals↗
PubMed1987

Involvement of the macrophage mannose-6-phosphate receptor in the recognition of Leishmania mexicana amazonensis.

Significant differences were found in the ability of resident mouse peritoneal macrophages to ingest amastigote and promastigote forms of Leishmania mexicana amazonensis. Differences in the association index of the parasites to the macrophages were also found between infective and non-infective promastigotes. Evidence was obtained suggesting that the macrophage receptor, which recognizes mannose-6-phosphate-containing units found in lysosomal enzymes, is involved in the association with the macrophage of promastigotes, but not of amastigotes. Addition of mannose-6-phosphate, its structural analogue fructose-1-phosphate, Hansenula holstii phosphomannan or the mannose-6-phosphate-containing lysosomal enzyme alpha-D-mannosidase to the interaction medium, markedly inhibits the association of the parasites with macrophages.

Animals↗
PubMed1996

Effects of fructose ingestion on sorbitol and fructose 3-phosphate contents of erythrocytes from healthy men.

To investigate the effect of fructose ingestion on sorbitol and fructose 3-phosphate (F3P) in erythrocytes, we administered 50 g fructose with and without treatment with an aldose reductase inhibitor, epalrestat, to seven healthy, normal-glucose-tolerant, male volunteers aged 20-43 years. The same subjects were given 50 g glucose on another day. The sorbitol and F3P contents in their erythrocytes increased significantly, reaching peak levels at 60 min and 180 min, respectively, following fructose in gestion. On the other hand, glucose ingestion did not cause any statistically significant change in sorbitol content in their erythrocytes, although it significantly elevated their F3P content. Treatment with epalrestat had no significant effect on incremental changes in erythrocyte sorbitol and F3P content following fructose ingestion. This suggests that oral fructose may be converted directly to sorbitol and F3P in erythrocytes instead of being converted via glucose. Thus, the dietary intake of fructose may affect the concentrations of sorbitol and F3P in erythrocytes in normal men.

Adult↗
PubMed1982

Diagnosis of Hunter's syndrome carriers; radioactive sulphate incorporation into fibroblasts in the presence or fructose 1-phosphate.

Mutual correction of co-cultivated fibroblasts from patients with Hunter's and Hurler's syndrome could be inhibited by either fructose 1-phosphate or mannose 6-phosphate. In the presence of fructose 1-phosphate a 50% mixture of fibroblasts from a patient with Hunter's syndrome and a normal homozygous individual showed an increased 35S-sulphate incorporation into acid mucopolysaccharides. When fibroblast cultures from one obligate and two possible carriers of Hunter's syndrome were tested for 35S-sulphate incorporation, the cultures showed either twice the normal 35S-sulphate incorporation into acid mucopolysaccharides in the presence of fructose 1-phosphate or an abnormally high incorporation in the presence as well as in the absence of the sugar phosphate.

Adult↗
PubMed1976

Time course of regeneration of minced frog muscles estimated by the level of energetic substrates.

1. Gastrocnemius muscles of frogs have been excised, chopped and put back into the leg. 2. The weight of the implanted muscles increases until the 8th day after the operation and then decreases to 1/3 of that of the control by the 30th day. 3. The inulin space is twice as high in regenerating muscle as in the unoperated controls. 4. Adenosine nucleotides are in an enzymatic equilibrium set by the ratio creatine/phosphorylcreatine during regeneration of the muscle. 5. Glycolytic intermediates (hexose monophosphate, fructose-1,6-diphosphate, alpha-glycerophosphate and lactate) have been measured during the course of muscle regeneration up to the 30th day. The results suggest that the glycolysis of regenerating muscle is very active. 6. The total creatine (sum of creatine and phosphorylcreatine) is very low after the operation: 5% of that of the controls; it rises sharply after the 8th day, and reaches 30% of that of the control on the 30th day. 7. The amount of total creatine seems proportional to the progress of the muscle regeneration. It is suggested to use this substance as a biochemical reference for biochemical works on muscle regeneration.

Adenine Nucleotides↗
PubMed1993

A possible case of transient hereditary fructose intolerance.

A patient is described who presented with the signs and symptoms of hereditary fructose intolerance a few hours after her first fructose challenge. The diagnosis was confirmed by the demonstration of reduced activity of hepatic aldolase B towards fructose-1-phosphate. A second liver biopsy 10 months later had normal aldolase B activity towards fructose-1-phosphate and a fructose tolerance test was also normal. A possible explanation for these findings is proposed.

Female↗