[Comparative study of methods for isolating glucose isomerase from Streptomyces albogriseolus mycelium]

Different procedures for disintegrating the biomass of Streptomyces albogriseolus were compared, and the recovery of glucose isomerase was analysed for each of the procedures. The following techniques were tested: disintegration of the mycelium with ultrasound and with pressure, autolysis in the presence of lysozyme and in its absence. The yields of the enzyme and total protein were found to depend on the time during which the biomass was treated. The effect of different procedures for isolating the enzyme on its recovery and activity is discussed.

The araIc mutation in Escherichia coli B/r

The araIc allele is a cis-acting mutation which has been used to define the araBAD promoter in Escherichia coli B/r. Nineteen araIc mutants were originally isolated by Englesberg and co-workers as Ara+ "revertants" of an araC deletion mutant (Englesberg et al. J. Mol. Biol. 43:281-298, 1969). The mutants constitutively expressed araBAD gene products in the absence of functional araC activator protein. Eight of the araIc mutations have been cloned by in vivo recombination onto pBR322-ara hybrid plasmids. Restriction and DNA sequence analysis of these araIc mutations showed that they result from a single base-pair change located at -35 in the araBAD promoter.

Some properties of D-mannose isomerase from Escherichia coli K12

A second-stage mutant of Escherichia coli K12 designated as strain 806 grew faster on D-lyxose than the mutant strain 805 previously described. Both mutants produced constitutively a novel enzyme, D-mannose isomerase, but strain 806 produced twice as much as strain 805. The enzyme could fortuitously convert D-lyxose to D-xylulose, which is a normal intermediate in the D-xylose catabolic pathway. The purified enzyme consisted of four subunits each with a molecular weight of about 40 000. In 0.14 M-Na2SO4, the tetramer dissociated completely into dimers. While the tetramer Km values for D-mannose and D-lyxose were 80 mM and 300 mM, respectively, the dimer Km values for these two sugars were both 300 mM. The amino acid composition of the enzyme was also determined.

Lactose and D-galactose metabolism in Staphylococcus aureus. II. Isomerization of D-galactose 6-phosphate to D-tagatose 6-phosphate by a specific D-galactose-6-phosphate isomerase

The inducible D-galactose-6-phosphate isomerase that functions in the metabolism of lactose and D-galactose in Staphylococcus aureus was partially purified from extracts of D-galactose-grown cells. It was shown to catalyze specifically the reversible isomerization of D-galactose 6-phosphate to D-tagatose 6-phosphate, the apparent Km values being 9.6 mM and 1.9 mM, respectively. At equilibrium, the ratio of D-galactose 6-phosphate to D-tagatose 6-phosphate was 9.0. The enzyme was not simulated by mono- or divalent cations and was not inhibited by EDTA, but it was inactivated reversibly by the thiol reagent N-ethylmaleimide. Its molecular weight was estimated to be about 100,000 both by gel filtration and by sedimentation in a sucrose density gradient. Data on stability, pH optimum, and inducibility of the enzyme are also presented. An improved procedure for the chemical synthesis of D-tagatose 6-phosphate is described, and resolution of the anomers of D-tagatose 6-phosphate by gas-liquid chromatography is reported.

Regulation of Escherichia coli K-12 hexuronate system genes: exu regulon

Two types of Escherichia coli K-12 regulatory mutants, partially or totally negative for the induction of the five catabolic enzymes (uronic isomerase, uxaC; altronate oxidized nicotinamide adenine dinucleotide: uxaB; mannonate hydrolyase, uxuA) and the transport system (exuT) of the hexuronate-inducible pathway, were isolated and analyzed enzymatically. Hexuronate-catabolizing revertants of the negative mutants showed a constitutive synthesis for some or all of these enzymes. Negative and constitutive mutations were localized in the same genetic locus, called exuR, and the following order for the markers situated between the min 65 and 68 was determined: argG--exuR--exuT--uxaC--uxaA--tolC. The enzymatic characterization of the pleiotropic negative and constitutive mutants of the exuR gene suggests that the exuR regulatory gene product exerts a specific and total control on the three exuT, uszB, and uxaC-uxaA operons of the galacturonate pathway and a partial control on the uxuA-uxuB operon of the glucuronate pathway. The analysis of diploid strains conatining both the wild type and a negative or constitutive allele of the exuR gene, as well as the analysis of thermosensitive mutants of the exuR gene, was in agreement with a negative regulatory mechanism for the control of the hexuronate system.

[Purification of glucosoisomerase from Lactobacillus brevis and its physico-chemical properties]

Glucosoisomerase isolated from disrupted cells of Lactobacillus brevis 74 by extraction with K, Na phosphate buffer was purified by step-by-step fractionation with (NH4)2SO4 and DEAE-cellulose chromatography. The purified enzyme was examined by polyacrylamide gel electrophoresis and ultracentrifugation. The examination showed the enzyme to be homogeneous. The sedimentation constant of the enzyme was found to be 8.3 S. The molecular weight of the enzyme was estimated to be 200 000. The presence of the carbohydrate moiety in the enzyme was demonstrated by qualitative methods.

Sequence of a yeast DNA fragment containing a chromosomal replicator and the TRP1 gene

The DNA sequence of a 1.45 kb EcoRI fragment from the yeast (Saccharomyces cerevisiae) TRP1 region has been determined. The fragment contains the TRP1 gene and a yeast chromosomal replicator. The TRP1 gene has been located on the fragment by analysis of potential initiation and termination codons in the DNA sequence. This location has been confirmed by subcloning portions of the fragment. Both the 5' and 3' noncoding regions of the TRP1 gene contain sequence homologies with analogous areas surrounding other yeast genes. The yeast replicator has been localized in a region near the 3' end of the TRP1 gene. The DNA sequence in this region contains several structural features which may be involved in the initiation of DNA replication.

[Amino acid composition and quaternary structure of glucosoisomerase (d-xylose-ketol-isomerase) from Actinomyces olivocinereus 154]

The amino acid composition of glucosoisomerase from Actinomyces olivocinereus 154 was investigated. The content of dicarboxylic acids--aspartic and glutamic--was found to be greater than that of basic acids--lysine, arginine and histidine. Hydrophobic acids were also detected to occur on appreciable quantities. No cysteine was seen in the enzyme. The experimental data on the effect of sodium dodecyl sulfate and urea suggests that the enzyme has a quaternary structure consisting of four nonidentical subunits.

Purification and some properties of hydroxypyruvate isomerase of Bacillus fastidiosus

Hydroxypyruvate isomerase of Bacillus fastidiosus is a novel enzyme (Braun, W. and Kaltwasser, H. (1979) Arch. Microbiol. 121, 129-134) which catalyzes the reversible conversion of tartronate semialdehyde into hydroxypyruvate. The enzyme was purified to homogeneity. The native molecule had a molecular weight of 265 000-280 000 and was composed of six subunits with a molecular weight of 45 000. The enzyme showed optimal activity at pH 6.6-7.4 and 57 degrees C. Hydroxypyruvate isomerase is stable on heating for 10 min at 67 degrees C. The enzyme appeared to be specific for tartronate semialdehyde and hydroxypyyruvate and no cofactors were involved in the reaction. The equilibrium constant K = [tartronate semialdehyde] divided by [hydroxypyruvate] was found to be 2.5 at pH 7.1, and 30 degrees C.

[Inhibition of glucose isomerase from Actinomyces olivocinereus 154 by polyols]

The inhibitory action of polyols, e. g. D-mannitol, D-glucitol, ribitol and xylitol, on the activity of glucose isomerase prepared from Actinomyces olivocinereus 154 was studied. All the polyols under study are purely reversible competitive inhibitors. The values of Ki for D-mannitol, D-sorbitol, D-arabitol, D-glucitol, ribitol and xylitol are 0.200, 0.140, 0.030, 0.024 and 0.020 M, respectively. The inhibition is to some extent decreased by increasing concentrations of the substrate and is completely abolished by increasing concentrations of Mg2+ and Co2+--up to 5.10(-2) and 5.10(-3) M, respectively.

Studies on the combined action of amylases and glucose isomerase on starch and its hydrolyzate. Part I. Production, extraction, purification and kinetic behavior of glucose isomerase

Glucose isomerase was produced from Streptomyces phaeochromogenes by aerobic fermentation at 28 degrees C for 24 hrs. The crude enzyme was obtained by disintegrating the harvested cells. It was found that ammonium sulphate at a saturation of 0.3-0.5 gave the maximum enzyme recovery (88.8%) from the crude extract, while acetone gave 66.2% at a concentration of 3/1 (V/V). On this basis the crude enzyme extract was purified following several steps as concentration, dialysis, precipitation with (NH4)2 SO4, then passing through column of Amberlite CG-50, and the eluate was treated with acetone to precipitate the enzyme. The kinetics behavior was studied and it was found that: optimum D-glucose concentration was 0.8 M, Km was 0.25 M, optimum pH was 7.0 and temperature was 70 degrees C. Magnesium at concentration of 0.07 M gave the maximum activity and its Km was 0.024 M. Antagonistic effects of Na+, Ca++ and Fe+++ in presence of 0.07 M of Mg++ were studied. Km and Vmax at different levels of Mg++ concentration were determined and no change in Km value was observed, while Vmax was affected. These findings indicate that the Mg++ combined with enzyme independently of the substrate.

[Conversion of D-glucose into D-fructose in a column reactor with immobilized glucose isomerase]

Conversion of D-glucose into D-fructose in a column reactor of a continuous type was studied using an immobilized enzyme, glucose isomerase from Actinomyces olivocinereus. The effective parameters of Km, Vmax, energy activation at various flow rates were calculated. During 32 days of continuous operation the enzyme activity fell down to 84% of the initial level. A system of recirculation was employed to use immobilized glucose isomerase with a low activity.

[Highly purified glucosoisomerase from Actinomyces olivocinereus 154]

The paper presents a method for producing highly purified glucosoisomerase from Actinomyces olivocinereus 154. The scheme of purification includes enzyme extraction from dry biomass, acetone fractionation, ammonium sulfate precicipation, and Sephadex G-200 chromatography. The highly purified enzyme is homogeneous as shown by polyacryl amide gel electrophoresis, analytical ultracentrifugation, and gel filtration. The highly purified enzyme has been prepared in a crystalline form. The molecular weight of the enzyme has been estimated by sedimentation equilibrium to be 162 000 and by gel filtration to be 158 000. The sedimentation constant of glucosoisomerase has been found to be 8.52 S.

[Preparation of protoplasts and localization of ribonuclease, beta-1,3-glucanase and glucosoisomerase in the fungal mycelium of Penicillium brevi-compactum]

Optimal conditions for the formation and isolation of protoplasts from the fungus Penicillium brevi-compactum were investigated. Localization of ribonuclease, glucosoisomerase and beta-1,3-glucanase in the mycelium was examined. To produce protoplasts, the mycelium was treated for 3-4 hours at 40 degrees C with the incubation mixture, containing chitinase from Actinomyces kurssanovii, lytic enzymes from Act. cellulose, lysozyme and 0.8 M mannitol as an osmotic stabilizer. The levels of activities of RNase, beta-1,3-glucanase, and glucosoisomerase were measured in the fungal mycelium before preparation of protoplasts, in the incubation mixture after their preparation, and in the protoplast lysate. The protoplast formation facilitated the release of RNase, beta-1,3-glucanase and glucosoisomerase from the fungal mycelium into the incubation mixture.

Metabolite gene regulation: imidazole and imidazole derivatives which circumvent cyclic adenosine 3',5'-monophosphate in induction of the Escherichia coli L-arabinose operon

Imidazole, histidine, histamine, histidinol phosphate, urocanic acid, or imidazolepropionic acid were shown to induce the L-arabinose operon in the absence of cyclic adenosine 3',5'-monophosphate. Induction was quantitated by measuring the increased differential rate of synthesis of L-arabinose isomerase in Escherichia coli strains which carried a deletion of the adenyl cyclase gene. The crp gene product (cyclic adenosine 3',5'-monophosphate receptor protein) and the araC gene product (P2) were essential for induction of the L-arabinose operon by imidazole and its derivatives. These compounds were unable to circumvent the cyclic adenosine 3',5'-monophosphate in the induction of the lactose or the maltose operons. The L-arabinose regulon was catabolite repressed upon the addition of glucose to a strain carrying an adenyl cyclase deletion growing in the presence of L-arabinose with imidazole. These results demonstrated that several imidazole derivatives may be involved in metabolite gene regulation (23).

Stabilization and purification of glucosamine 6-phosphate isomerase from rat kidney

1. Glucosamine 6-phosphate (GlcN-6-P) isomerase of rat kidney was resistant to heating at 50--55 degrees in crude extract but not after several purification steps. GlcN-6-P and N-acetylglucosamine 6-phosphate were found to stabilize the isomerase under these conditions. They also protected the enzyme from tryptic digestion, but only GlcN-6-P was effective against inactivation by p-chloromercuribenzoate. 2. When GlcN-6P isomerase was purified from fresh kidney and kidney stored at -20 degrees, separately and under GlcN-6-P, the two preparations were different in elution profile from a hydroxyapatite column. It was subsequently found that storage of crude extract at -20 degrees resulted in molecular alterations of the enzyme. Prolonged purification appeared to affect the enzyme similarly. The molecular alterations, however, were suppressed if the extract was stored at -70 degrees. 3. These findings have been utilized to develop a procedure, which enables us to purify rat kidney GlcN-6-P isomerase without any molecular alteration and in good yield.

Inhibition of ribose-5-phosphate isomerase by 4-phosphoerythronate

Hoping to exploit the special affinity of enzymes for unstable intermediates in substrate transformation, we have determined the effectiveness of possible analogs of ene-diolate intermediates as inhibitors of spinach ribose-5-phosphate isomerase. 4-Phosphoerythronic acid was found to be a very strong competitive inhibitor, with a Ki value almost 3 orders of magnitude lower than the Km value of ribose 5-phosphate, and very much lower than the Ki value of any other inhibitor that was examined.

Regulation of glucosamine-6-phosphate deaminase synthesis in yeast

A basal level of glucosamine-6-phosphate deaminase is detected in yeast cells grown on glucose. However, a burst of enzyme production occurs in the presence of N-acetylglucosamine in pathogenic Candida albicans and non-pathogenic Saccharomyces cervisiae. The enzyme synthesis stops and its concentration in the cells declines rapidly as soon as N-acetylglucosamine is removed from the medium. Experiments with RNA- and protein-synthesis inhibitors indicate that the appearance of new enzyme activity is dependent on concomitant new protein synthesis and the inducer operates at a transcriptional level. However, inhibition of DNA synthesis either by hydroxyurea or by mitomycin-C does not impair the synthesis of glucosamine-6-phosphate deaminase.

Glucosamine metabolism in Drosophila salivary glands. Separation of metabolites and some characteristics of three enzymes involved

The conversion of fructose 6-phosphate to mucopolysaccharide precursors was studied in extracts of Drosophila virilis salivary glands. 1. Methods for chromatography of sugar phosphates were adapted and modified to allow routine separation and quantitation of radioactivity of the metabolites from milligram amounts of tissue. Anion exchange chromatography was performed on Dowex 1-X8 employing steps of increasing ammonium formate. Final isolation of each compound was achieved by various thin-layer chromatographic systems. 2. Data obtained by isotope incorporation into glucosamine 6-phosphate compare well with results of the Morgan-Elson colorimetric assay for amino-sugars. 3. Glucosaminephosphate isomerase (glutamine-forming) (EC 5.3.1.19) in gland extracts has a Km of 0.35 mM for fructose 6-phosphate, and of 0.25 mM for glutamine. The enzyme is inhibited at glutamine concentrations exceeding 1 mM and by UDP-N-acetylglucosamine (50% at 0.6 mM). Feedback inhibition by UDP-N-acetylglucosamine is enhanced by AMP and by glucose 6-phosphate. 4. Glucosaminephosphate isomerase (EC 5.3.1.10) has a twenty fold lower affinity towards fructose 6-phosphate (Km = 6.0 mM) compared to the glutamine-forming isomerase. Km (NH+4) is 7.4 mM. In the presence of 20 mM glucose 6-phosphate, the pH optimum is shifted from 6.6 to 7.4, and V increased by a factor of 2.5. Furthermore, the affinity is approximately doubled for both substrates. 5. Glucosamine acetyltransferase (EC 2.3.1.3) has a Km of 2 mM for glucoseamine 6-phosphate. Its activity is not rate-limiting in salivary glands. Since N-acetylglucosamine 6-phosphate and 1-phosphate were found near equilibrium concentrations, acetylglucosamine phosphomutase (EC 2.7.5.2) must also be present in the extracts.

The shape of L-arabinose isomerase from Escherichia coli

L-Arabinose isomerase, EC 5.3.1.4, catalyzes the conversion of L-arabinose to L-ribulose, the first step in the catabolism of L-arabinose by Escherichia coli B/r. Patrick and Lee (1969) J. Biol. Chem. 244, 4277--4283) demonstrated that native L-arabinose isomerase is composed of six identical subunits of approximately Mr = 60,000. In this paper we describe an electron microscopy study of the arrangement of the six identical subunits. The isomerase is seen in two distinctly different orientations. The first has three subunits visible, with a 3-fold axis of symmetry, corresponding to a face-on view of two stacked, eclipsed trimers. The second orientation is rectangular in shape with 2-fold symmetry; suggesting a side-on view of the stacked trimers. The six identical subunits are thus arranged with D3 symmetry as in a trigonal prism. Measurements were made on the maximum profile of the three 2-fold axes of symmetry of the face-on orientations, and of both the long and short dimensions of the side-on orientation. The best estimate for the maximum profile of the 2-fold axes of symmetry of the face-on view is 106 +/- 8 A, using glutamine synthetase as an internal size standard. Measurements from micrographs of the isomerase alone, using an external magnification calibration, give the following results: for the maximum profile of the three 2-fold axes of symmetry of the face-on view, 132 +/- 7 A; for the long axis of the side-on view, 136 +/- 10 A; and for the short axis, 105 +/- 6 A. These measurements are consisting with the interpretation of the profiles as representing two different orientations of the L-arabinose isomerase.

Purification, crystallization, and properties of D-ribose isomerase from Mycobacterium smegmatis

D-Ribose isomerase, which catalyzes the conversion of D-ribose to D-ribulose, was purified from extracts of Mycobacterium smegmatis grown on D-ribose. The purified enzyme crystalized as hexagonal plates from a 44% solution of ammonium sulfate. The enzyme was homogenous by disc gel electrophoresis and ultracentrifugal analysis. The molecular weight of the enzyme was between 145,000 and 174,000 by sedimentation equilibrium analysis. Its sedimentation constant of 8.7 S indicates it is globular. On the basis of sodium dodecyl sulfate gel electrophoresis in the presence of Mn2+, the enzyme is probably composed of 4 identical subunits of molecular weight about 42,000 to 44,000. The enzyme was specific for sugars having the same configuration as D-ribose at carbon atoms 1 to 3. Thus, the enzyme could also utilize L-lyxose, D-allose, and L-rhamnose as substrates. The Km for D-ribose was 4 mM and for L-lyxose it was 5.3 mM. The enzyme required a divalent cation for activity with optimum activity being shown with Mn2+. the Km for the various cations was as follows: Mn2+, 1 times 10(-7) M, Co2+, 4 times 10(-7) M, and Mg2+, 1.8 times 10(-5) M. The pH optimum for the enzyme was 7.5 to 8.5. Polyols did not inhibit the enzyme to any great extent. The product of the reaction was identified as D-ribulose by thin layer chromatography and by preparation of the O-nitrophenylhydrazone derivative.

Subunit structure and amino acid composition of xylose isomerase from Streptomyces albus

The subunit structure and amino acid composition of xylose isomerase from Streptomyces albus have been examined. A native molecular weight of 165,000 determined by sedimentation equilibrium was reduced to 43,000 when the protein was treated with 6 M guanidine hydrochloride. No further reduction in molecular weight was observed when potential disulfide bridges of xylose isomerase were reduced and alkylated, indicating that the protein was devoid of interchain disulfide bonds. NH2-terminal analysis using [3H]dansyl chloride showed 0.86 residues of methionine per Mr equals 41,500 unit. Analysis of the native protein with an automated protein sequenator revealed the presence of only one degradable polypeptide chain. Fractionation of the soluble tryptic peptides of S-[14C]carboxymethyl xylose isomerase by ion exchange chromatography and one-dimensional paper electrophoresis yielded 37 to 43 peptides. When the acid-insoluble tryptic peptides were dissolved and analyzed using gel filtration techniques, and additional four peptides were found. A unique radioactive tryptic peptide containing S-carboxymethylcysteine was found among the soluble peptides, confirming cysteine as the limiting amino acid residue in the amino acid composition of xylose isomerase. On the basis of its lysine and arginine content, the number of tryptic peptides is consistent with the hypothesis that the native xylose isomerase is a tetramer of four very similar or identical subunits of Mr equals 41,500, associated by noncovalent bonds.

Two ribose-5-phosphate isomerases from Escherichia coli K12: partial characterisation of the enzymes and consideration of their possible physiological roles

Two physically and genetically distinct forms of ribosephosphate isomerase have been identified in Escherichia coli K12. The constitutive ribosephosphate isomerase A has a Km for ribose 5-phosphate (4.4 +/- 0.5 mM) six times greater than that of the inducible ribosephosphate isomerase B (0.83 +/- 0.13 mM). Treatment of the enzymes with 1.25 mM iodoacetate resulted in 100% loss of activity for ribosephosphate isomerase B, whereas ribosephosphate isomerase A was unaffected. Various cellular metabolites were tested and found to be without significant effect on either enzyme. The two enzymes could be separated by filtration on Sephadex G75 superfine and their apparent molecular weights were 45000 for ribosephosphate isomerase A and 32000-34000 for ribosephosphate isomerase B. Under certain conditions the two enzymes showed different patterns of heat inactivation but the results with ribosephosphate isomerase A varied in an unusual way with the protein concentration. Ribosephosphate isomerase B was formed inducibly in a mutant lacking ribosephosphate isomerase A but there was no evidence for the production of ribosephosphate isomerase B in wild-type cells. The formation of ribosephosphate isomerase B was not a consequence of the ribosephosphate isomerase B mutation, since strains could be constructed which formed both enzymes constitutively in the anticipated amounts. The ribosephosphate isomerase formed by a secondary mutant obtained from a ribosephosphate-isomerase-A-negative strain was identified as ribosephosphate isomerase B on the basis of its Km, elution profile from Sephadex G75, inhibition of iodoacetate, and heat inactivation. The ribosephosphate isomerases of another Escherichia coli K12 strain, X289, were investigated, since their properties were reported to be different from many of these described here for ribosephosphate isomerases A and B. In our hands strain X289 contained two ribosephosphate isomerases apparently identical to ribosephosphate isomerases A and B. The evidence to date suggests that ribosephosphate isomerase A catalyses the formation of ribose 5-phosphate from ribulose 5-phosphate and also participates in the reverse reaction during ribose and adenosine catabolism. The normal physiological role of the inducible ribosephosphate isomerase B is still uncertain.