Distribution of coenzyme B12-dependent diol dehydratase and glycerol dehydratase in selected genera of Enterobacteriaceae and Propionibacteriaceae

The presence of diol dehydratase and glycerol dehydratase was shown in several bacteria of Enterobacteriaceae grown anaerobically on 1,2-propanediol and on glycerol, respectively. Diol dehydratases of Enterobacteriaceae were immunologically similar, but distinct from that of Propionibacterium freudenreichii.

Amino acid sequence of the biotinyl subunit from transcarboxylase

The complete amino acid sequence of the biotinyl subunit from the enzyme transcarboxylase of Propionibacterium shermanii has been determined from the structures of overlapping tryptic and cyanogen bromide peptides together with sequenator analysis on the whole subunit. The subunit contains 123 amino acid residues. Eleven of nineteen residues in the region of biotin attachment, when compared to pyruvate carboxylase from avian liver (Rylatt, D. B., Keech, D. B., and Wallace, J. C. (1977) Arch. Biochem. Biophys. 183, 113-122), were found to be in identical positions relative to biocytin. There was less homology with acetyl-CoA carboxylase from Escherichia coli (Sutton, M. R., Fall, R. R., Nervi, A. M., Alberts, A. W., Vagelos, P. R., and Bradshaw, R. A. (1977) J. Biol. Chem. 252, 3934-3940), but in all of these biotin enzymes there was an alanylmethionyl-biocytinyl-methionine sequence. The secondary structure of the biotinyl subunit has been estimated using the method of Chou and Fasman (Chou, P. Y., and Fasman, G. D. (1978) Adv. Enzymol. 47, 45-148) and considered in relationship to the role of the biotinyl subunit in the structure and function in transcarboxylase.

[Study and differentiation of some hydrolases active on triglycerides and esters, in anaerobic bacteria, using gas liquid chromatography (author's transl)]

Anaerobic bacteria are classified using presence or absence of phospholipase and lipase, among other criteria. Techniques are described for the qualitative and quantitative detection of bacterial esterases (carboxylic ester hydrolase) and lipases (triacylglycerol acyl hydrolase) endo- or -exocellular, using gas liquid chromatographic method. Results with representatives anaerobic species are briefly presented.

Production of hyaluronidase by propionibacteria from different origins

114 strains of anaerobic and microaerophilic coryneform bacteria from different origins were investigated for production of free extracellular hyaluronidase (hyaluronate glycanohydrolase, EC 3.2.1.36). A quantitative technique was applied measuring the release of N-acetyl-glucosamine groups from purified human potassium hyaluronate. The strains belonged to the following species: Propionibacterium acnes, P. avidum, P. granulosum, P. lymphophilum, the formerly so-called Corynebacterium parvum, P. freudenreichii subsp. freudenreichii and shermanii, P. thoenii, P. acidi-propionici, C. minutissimum, and Arachnia propionica. All together, 59 out of 114 (approximately 51.8%) tested strains showed clearly measurable hyaluronidase activities. P. acnes, the propionibacterium species most frequently found in acne vulgaris lesions, proved to be the most active species tested, 44 out of 64 (approximately 68.8%) P. acnes strains being positive. 5 strains producing hyaluronate glycanohydrolase activities of more than 60 mU/ml in thioglycollate broth cultures could be detected. P. avidum and P. granulosum strains were positive in only 45.0% and 33.3%, respectively, and their mean hyaluronidase activities were significantly lower. Differences in hyaluronidase activities of P. acnes strains isolated from acne vulgaris lesions and strains from normal human skin could not be found. The possible pathogenic role of propionibacteria hyaluronidase in acne vulgaris is discussed.

[Participation of methylcobalamin in the methylation of Propionibacterium shermanii DNA]

Propionibacterium shermanii is characterized by a high content of 5-methylcytosine (5 MC). The level of 5-MC in B12-deficient cells of the culture is twice as low as in the control. The in vitro treatment of DNA isolated from the B12-deficient cells with methyl-cobalamin in the presence of the extract of control cells possessing the activity of DNA-methylase increases the content of 5-MC to the control level. No additional methylation of DNA in vitro takes place in the absence of the methylase system and in the presence of other forms of corrynoids. The methylating activity is displayed either in the presence of methionine or without it. The inhibitor of methylcobalamin, i.e. diftorchlormethyl-cobalamin, blocks methylation of DNA. Small quantities of S-adenosylmethionine are necessary for the reaction of methylation.

A rapid, enzymatic assay for the measurement of inorganic pyrophosphate in animal tissues

A simple, rapid enzymatic assay for the determination of inorganic pyrophosphate in tissue and plasma has been developed using the enzyme pyrophosphate--fructose-6-phosphate 1-phosphotransferase (EC 2.7.1.90) which was purified from extracts of Propionibacterium shermanii. The enzyme phosphorylates fructose-6-phosphate to produce fructose-1,6-bisphosphate using inorganic pyrophosphate as the phosphate donor. The utilization of inorganic pyrophosphate is measured by coupling the production of fructose-1,6-bisphosphate with the oxidation of NADH using fructose-bisphosphate aldolase (EC 4.1.2.13), triosephosphate isomerase (EC 5.3.1.1), and glycerol-3-phosphate dehydrogenase (NAD+)(EC 1.1.1.8). The assay is completed in less than 5 min and is not affected by any of the components of tissue or plasma extracts. The recovery of pyrophosphate added to frozen tissue powder was 97 +/- 1% (n = 4). In this assay the change in absorbance is linearly related to the concentration of inorganic pyrophosphate over the curvette concentration range of 0.1 microM to 0.1 mM.

Synergistic lysis of erythrocytes by Propionibacterium acnes

Sheep and human erythrocytes, partially processed by Staphylococcus aureus or Clostridium perfringens, were susceptible to lysis in the presence of Propionibacterium acnes. P. acnes liberated a lipase that was detected on Tween 80 agar and also on phospholipase C-precipitated egg yolk agar. Such a lipase might have contributed in the process of an intensified cellular lysis. Similar reactions were attempted with Lactobacillus acidophilus, known to possess a nondiffusible lipase, and failed to produce any such reactions. The synergistic reactions, between P. acnes and C. perfringens, were compared with The classical CAMP reaction in an attempt to find a correlation with the established membrane composition of the erythrocytes involved. Synergistic reactions observed do seem to reflect the membrane composition. Such findings, besides being contributory to an understanding of the role of these organisms in the process of pathogenesis, are of importance in the elucidation of molecular organization of biomembranes. Detailed studies, involving a large number of representative anaerobic bacteria, may also help provide an avenue in anaerobic species identification.

Electrophoretic protein patterns and enzyme mobilities in anaerobic coryneforms

The soluble protein patterns and electrophoretic mobilities of malate and succinate dehydrogenases and catalase have been examined in 25 strains of Propionibacterium acnes, P. granulosum, and P. avidum. A distinctive protein pattern for each species was found, and it was possible also to distinguish the serotypes within P. acnes and P. avidum. Strains of P. acnes, P. granulosum, and P. avidum could be differentiated by the mobilities of their malate dehydrogenases. Catalase activity was detected in the soluble fractions of all strains. Catalases from P. acnes and P. avidum strains had the same mobility, whereas that from P. granulosum was slightly slower. Under the conditions used, succinate dehydrogenase activity could be detected, but the patterns were not distinctive.

Investigation of the mechanism of the methylmalonyl-CoA mutase reaction with the substrate analogue: ethylmalonyl-CoA

1. Ethylmalonyl-CoA was found to be a substrate for methylmalonyl-CoA mutase from Propionibacterium shermanii, the product being mainly (2R)-methylsuccinyl-CoA along with some (2S)-diastereoisomer. 2. The relevant 1H-nuclear magnetic resonance signals of methylsuccinic acid and of its dimethyl ester were assigned to the diastereotopic methylene hydrogens using sterospecifically dideuterated specimens of known configuration. 3. [2(-2)H1]Ethylmalonyl-CoA was converted by methylmalonyl-CoA mutase in 2H2O mainly to (2R, 3S)-[3(-2)H1]methylsuccinyl-CoA. No dideuterated product was observed. 4. Starting from (1R)-[1(-2)H1]-ethathanol, (1S)-[1(-2)H1]ethanol and [2H6] ethanol the following deuterated specimens of ethylmalonic acid were synthesised and characterised: (3S)-[3(-2)H1], (3R)-[3(-2)H1] and [3(-2)H2, 4(-2)H3], respectively. 5. Conversion of (3S)-[3(-2)H1]-ethylmalonyl-CoA (70% 2H1 and 2% 2H2 species) on the mutase in water afforded mainly (2R)-[2(-2)H1]methylsuccinyl-CoA along with some (2S)-diastereoisomer. No deuterium loss was observed. 6. Methylmalonyl-CoA mutase converted (3R)-[3(-2)H1]ethylmalonyl-CoA (81% 2H1 and 2% 2H2 species) to the following methylsuccinyl-CoA species: 33% [3(-2)H1], the deuterium being in the threo position with respect to the methyl group; 21% [2(-2)H1]; 46% unlabelled. The ratio of the species with (2R) and (2S) configuration was about 60:40. 7. Reaction of [3(-2)H2, 4(-2)H3]ethylmalonyl-CoA (94.5% [2H5] species) with the mutase gave the following labelled methylsuccinyl-CoA species:53.4% [methyl-2H3, 2(-2)H1, 3(-2)H1], the 3-deuterium being in the threo position with respect to the methyl group; 37.6% [methyl-2H3, 2(-2)H1]; 5% [methyl(-2)H3, 2(-2)H1, 2(-2)H1, 3(-2)H1] the 3-deuterium being in erythro position with respect to the methyl group; 4% [methyl(-2)H3, 3(-2)H1]. The ratio of the species with (2R) and (2S) configuration was about 70:30. 8. Implications of these findings for the mechanism of the rearrangements catalysed by coenzyme B12 are discussed.

A comparison of the malate dehydrogenase of the propionic acid bacteria with the mammalian soluble and mitochondrial isoenzymes

1. Like the malate dehydrogenases of eucaryotic cells, the Propionibacterium shermanii enzyme is a dimer consisting of two 35,000 molecular weight subunits. 2. In electrophoretic behavior, resistance to substrate inhibition and stability to heating and dilution the P. shermanii MDH is more similar to the s-MDH than to the m-MDH of pig heart. 3. The P. shermanii MDH has a high turnover number (ca. 140,000) as well as Km values for both L-malate and oxalacetate which are four times higher than the mammalian isoenzymes. 4. A coupled assay for MDH using the malate-lactate transhydrogenase and diaphorase is described in which both substrates, L-malate and NAD, are regenerated.

A study on nitrate reductase from Propionibacterium acidi-propionici

Cell extract from a strain of Propionibacterium acidi-propionici with high nitrate reductase (NaR) activity catalyzed nitrate reduction with glycerol phosphate, NADH, or lactate. The reaction was inhibited partially by fumarate or oxygen. NaR linked to methyl viologen was found mostly in particulate fractions. It was solubilized by treatment with Emulgen 810 and purified 46-fold by DEAE-cellulose, Sepharose 4B, and triple DEAE-Sephadex chromatographies in the presence of the detergent. It was rather labile but was stabilized by glycerol. The molecular weight was estimated to be 230,000 by Sepharose 4B gel filtration and the isoelectric point was pH 5.0-5.5. The pH optimum was at 6.5-7.5 and Km for nitrate was 0.1 mM. As electron donors, methyl and benzyl viologen were utilized well but FAD and FMN were fairly ineffective. Chlorate was an active acceptor as well as nitrate. Azide, cyanide, and thiocyanate inhibited NaR. On adding 1 mM tungstate to the growing medium, the NaR level in grown cells was lowered; addition of 0.01 mM molybdate restored the activity partially. NaR is suggested to be a molybdo-protein, similar to this enzyme from other bacteria.

Effects of oxygen on Propionibacterium shermanii grown in continuous culture

Growth yields, enzyme activities, cytochrome concentrations and the rates of product formation were determined in Propionibacterium shermanii cultures grown in a chemostat with lactate as the energy source at various concentrations of oxygen. Oxygen was toxic when its partial pressure in the inflowing gas was just sufficient to give measurable dissolved oxygen concentration in the culture, when it inhibited lactate oxidation and NADH oxidase activity. Below this oxygen concentration, P. shermanii behaved as a facultative anaerobe. The adaptation from anaerobic metabolism to aerobic metabolism, however, was complex. Low partial pressures of oxygen led to decreased cytochrome and membrane-bound dehydrogenase activities and molar growth yield. Above an oxygen partial pressure of 42 mmHg in the inflowing gas stream, these changes were reversed, leading to an aerobic type of metabolism. At the highest subtoxic concentration of oxygen used (330 mmHg in the input gas), lactate was oxidized mainly to acetate and carbon dioxide and the rate of propionate formation was very low. The high molar growth yield obtained under these conditions suggested that lactate and NADH oxidation via the cytochrome electron transport system was coupled to ATP synthesis.

Purification of methylmalonyl-CoA mutase from Propionibacterium shermanii using affinity chromatography

A novel procedure for the purification of methylmalonyl-CA mutase from Propionibacterium shermanii has been described which employs affinity chromatography on a column of immobilized vitamin B-12 linked covalently to Sepharose. The method has the advantage of being simple and rapid, thus enabling the purification of the enzyme to near homogeneity with good yields.

Association-dissociation of transcarboxylase

Transcarboxylase consists of a central subunit to which two sets of three subunits each are attached at opposite faces. Evidence obtained by various ultracentrifugal techniques has shown that there is an equilibrium between active forms of the enzyme with six, five, four, three, two, and one subunits attached to the central subunit. Since each attached subunit contains two biotins, the biotin content of these forms varies from 12 to 2. By reactive enzyme sedimentation at pH 5.5, it has been shown that the largest form of the enzyme (with 12 biotins and a molecular weight of 1.2 X 10(6) is active and that at pH 6.8 this form of the enzyme dissociates to an enzymatically active form containing three attached subunits. This result is in accord with previous observations (Wood, H.G., Chiao, J.P., and Poto, E.M.(1977), J Biol. Chem. 252, 1490; Wrigley, N.G., Chiao, J.P., and Wood, H.G. (1977), J Biol. Chem. 252, 1500) which showed that dissociation of three of the six attache subunits occurs preferentially from one face of the central subunit and that the remaining three attached subunits are quite firmly bound to the second face of the central subunit. Multiple peaks are obtained in sedimentation velocity experiments at 60 000 rpm because the rate of sedimentation outstrips the rate of equilibration of the different forms of transcarboxylase, whereas at 30 000 rpm a single peak of the multiple form of the enzyme is observed, since equilibration of the different forms keeps abreast of the sedimentation. The rate and extent of dissociation are increased by increase in temperature. It has been shown by centrifugation under oil that the association-dissociation of the large form of the enzymes with six, five, and four attached subunits is not affected by hydrostatic pressure. In contrast, the association-dissociation of the enzyme with three and two attached subunits appears to be affected by pressure. The accumulated results indicate that the native form of the enzyme in the cytosol of the cell consists of a series of enzymatically active forms with one to six attached subunits. The predominant forms in the cytosol will depend on the concentration of the constituent subunits, the pH, the concentration of ions (particularly divalent anions), and the temperature.

A new large form of transcarboxylase with six outer subunits and twelve biotinyl carboxyl carrier subunits

A new form of transcarboxylase has been isolated which has a molecular weight of 1,200,000, an s20,w of 26 S, and contains 12 biotinyl groups. Transcarboxylase as isolated previously has a molecular weight of 790,000, an s20,w of 18 S, and contains six biotinyl groups. The larger species of enzyme consists of a central hexameric subunit with six dimeric outer subunits attached to it by biotinyl carboxyl carrier proteins, three each at the opposite faces of the central subunits. This larger species is stable at pH 5.5, but dissociates to the 18 S species at pH values near neutrality with loss of a set of three of the outer subunits with two of the biotinyl carboxyl carrier proteins still attached to each of these subunits. The dissociation to the 18 S form occurs by several rapidly reversible steps and under certain conditions of centrifugation multiple peaks are observed as a consequence of the occurrence of different forms of enzyme with variable numbers of the outer subunits attached to the 18 S enzyme. The s20,w value of the so-called 26 S enzyme varies with conditions. Isolated 18 S enzyme has been combined with isolated outer subunits to form active 26 S enzyme. The newly enzyme is a normal form but has not been isolated previously because of its dissociation to the 18 S form at neutral pH. A procedure is described for the isolation of the 26 S form in a highly purified state. The molecular weight of the enzyme has been determined by high speed meniscus depletion. In addition, a procedure is described for dissociation of the 26 S form of the enzyme and isolation of the resulting outer subunits with the biotinyl subunits still attached to it. Evidence is presented that all six outer subunits participate in the enzymatic reaction which includes the demonstration that; (a) all 12 biotins of the 26 S form of the enzyme can be carboxylated with [3-14C]methylmalonyl coenzyme A; (b) there is an increase in enzymatic activity when the outer subunits are combined with the normal 18 S enzyme with formation of the 26 S enzyme; and (c) a 26 S form of the enzyme is active which is prepared by combination of inactive 18 S trypsin-treated transcarboxylase with the outer subunits. The trypsin-treated 18 S enzyme is inactive because trypsin removes the biotin as biotinyl peptides and the 26 S enzyme is active because of the second set of active outer subunits.

Electron microscopy of the large form of transcarboxylase with six attached subunits

In this paper we show that the native form of transcarboxylase may be a species which has six rather than three subunits attached to the central subunit. We have designated this form as the 26 S enzyme. Electron micrographs support the view that the six subunits are attached in sets of three at the opposite faces of the central subunit, in contrast to the 18 S form in which all three subunits appear to be attached only at one face. In addition, evidence is presented that the dissociation of the 26 S to the 18 S form of transcarboxylase occurs with the loss of three subunits exclusively from one face of the central subunit. This result may indicate that the two faces of the central subunit differ structurally or there is negative cooperativity in the dissociation of subunits. The 26 S transcarboxylase, which was made by attachment of subunits to the 18 S enzyme or trypsin-treated 18 S enzyme was shown to have subunits on both faces of the central subunit. Treatment of the 26 S enzyme with carbodimide to cross-link the subunits to the central subunit and thus stabilize the structure resulted in improved electron micrographs. A model of the 26 S form of the enzyme is presented.

Steady state and exchange kinetics of pyruvate, phosphate dikinase from Propionibacterium shermanii

Evidence is presented based on requirements for exchange in the partial reactions, initial velocity and exchange kinetics and product inhibition, that the pyruvate, phosphate dikinase reaction of propionibacteria occurs by a nonclassical Tri Uni Uni Ping Pong mechanism. The mechanism involves a pyrophosphoryl enzyme, a phosphoryl enzyme, and the free enzyme, and three functionally distinct and independent substrate sites. On the first site, there is pyrophosphorylation of the enzyme by ATP with subsequent release of AMP. The pyrophosphoryl moiety then reacts at the second site with Pi yielding the product PPi and the phosphoryl from of the enzyme. At the third site pyruvate is phosphorylated yielding P-enolpyruvate and the free enzyme. The three catalytic sites are proposed to be linked by a histidyl residue which functions as a pyrophosphoyrl- and phosphoryl-carrier between the three sites. This proposal is based on the following observations. (A) The patterns of the double reciprocal plots of the initial velocities were all parallel; (b) product inhibition between each pair of substrates and products of the three partial reactions were competitive, i.e. ATP against AMP, Pi against PPi, and pyruvate against P-enolpyruvate; (c) the other product inhibitions, with one exception, were noncompetitive as required by the nonclassical ping-pong mechanism; (d) ATP or P-enolpyruvate was required for the Pi in equilibrium PPi exchange reaction which is in accord with the participation of a pyrosphosphoryl or phosphoryl form of the enzyme in this exchange; (e) the ATP in equilibrium AMP exchange and pyruvate in equilibrium P-enolpyruvate exchange did not require additional substrates. In addition, the inhibition and participation in the exchange reactions of the alpha,beta and beta,gamma-methylene analogues of ATP and of the methylene analogue of inorganic pyrophosphate were investigated and the results were in accord with the proposed mechanism. The combined evidence provides a well documented example of a three site nonclassical Tri Uni Uni Ping Pong mechanism.

Immunochemistry of the subunits of transcarboxylase

Antisera reactive with the subunits of transcarboxylase were produced by injecting rabbits with the 12 SH and 5 SE subunits prepared from trypsin-treated enzyme and with the 12 SH subunit prepared from native transcarboxylase by avidin-Sepharose chromatography. Biotinyl peptides (46 and 65 amino acid residues), released from the enzyme by brief trypsin treatment, formed complexes with avidin and this noncovalent conjugate was used as an antigen to prepare antibodies reactive with the 1.3 SE biotin carboxyl carrier protein. All of these antisera were capable of inhibiting and precipitating intact transcarboxylase. In competitive binding experiments utilizing enzyme inhibition to detect antibody binding, it was found that only the 5 SE subunit was capable of preventing the anti-5 SE sera from inhibiting the enzyme. This technique is useful as a rapid, specific assay for the 5 SE subunit. Both the 5 SE and 12 SH subunits were capable of preventing the anti-12 SH sera from inhibiting the enzyme. To further study this apparent cross-reactivity, the antisera were tested for their capacity to inhibit the partial reactions of transcarboxylase as catalyzed by the isolated subunits. These studies revealed that the anit-12 SH serum inhibits the partial reaction catalyzed by the 12 SH subunit, but preincubation with the 5 SE subunit does not relieve this inhibition, confirming that specific antibody against the 12 SH subunit was formed. These studies also showed that the anti-12 SH serum could inhibit the 5 SE partial reaction, apparently demonstrating cross-reactivity with the 5 SE subunits of the intact enzyme. A panel of immunologic methods was used to characterize the cross-reactivity and quantitate any cross-contamination of the subunit preparations. Passive hemagglutination-hemagglutination inhibition, double immunodiffusion in gels, and competitive precipitation of radioactive antigen all demonstrated cross-reactivity between the isolated subunits and the antisera. Although the subunit preparations apparently are cross-contaminated to a minor extent, this seems insufficient to account for the quantitative aspects of the immunologic cross-reactivity of the subunits with the antisera. Structural homology between the subunits of transcarboxylase is considered to be responsible for the observed cross-reactivity.

Aldolases of the lactic acid bacteria. Demonstration of immunological relationships among eight genera of Gram positive bacteria using an anti-pediococcal aldolase serum

Reciprocal qualitative and quantitative immunological experiments employing an anti-Pediococcus cerevisiae aldolase serum confirmed many of the interspecific relationships demonstrated previously among lactic acid bacteria with antisera prepared against the Streptococcus faecalis fructose diphosphate aldolase. The extent of immunological relatedness observed between the Lactobacillus and Pediococcus aldolases was markedly gses indicating that the pediococci share closer phylogenetic ties with the rod-shaped lacotbacilli than with their spherical counterparts in the streptococci. In addition to confirming the existence of definitive, but distant, relationships between the lactic acid bacteria and certain gram positive nonsporeforming anaerobes, immunological cross-reactivity was also demonstrated between the pediococcal aldolases and those of Aerococcus viridans.

Lactate metabolism in Propionibacterium pentosaceum growing with nitrate or oxygen as hydrogen acceptor

When anaerobic cultures of Propionibacterium pentosaceum were shifted to low dissolved-oxygen concentration (D.O.C.), acetate production from lactate diminished and propionate production stopped, whereas pyruvate accumulated and oxygen was consumed. Assuming that energy is generated in the electron transfer to oxygen, YATP values (g dry wt bacteria/mole ATP) of between 7.2 and 11.9 were calculated from molar growth yields and product formation. When oxidative phosphorylation in the electron transfer to oxygen was ignored, unreasonably high YATP values were obtained. From these results it is concluded that energy is indeed generated in the electron transfer to oxygen. However, synthesis of cytochrome b was strongly repressed by oxygen. Furthermore, synthesis of all catabolic enzymes studied was impaired in bacteria growing at low D.O.C. Thus, the anaerobic character of P. pentosaceum may be explained by the inhibition of synthesis of both cytochrome b and enzymes in the presence of oxygen. It was demonstrated that nitrate reductase is synthesized constitutively in P. pentosaceum. Synthesis of nitrate reductase was stimulated by nitrate and repressed by oxygen. Synthesis of fumarate reductase was also repressed by oxygen, whereas only a small effect of nitrate on this enzyme was observed. However, propionate formation is inhibited during growth with nitrate. The absence of propionate formation in the presence of oxygen and nitrate is explained by inavailability of NADH needed for the conversion of oxaloacetate into malate in the reductive pathway to succinate, so that succinate and propionate cannot be formed.

Tetrapyrrole biosynthesis: N-methyl-N'-nitrosoguanidine-induced mutants of Propionibacterium shermanii

An isolation method forN-methyl-N′-nitrosoguanidine-induced catalase negative mutants ofP. shermaniibased on replica plating is described. In contrast to previous methods, it extends to the early stages of tetrapyrrole biosynthesis which are common in both corrins and porphyrins. It may thus aid in elucidating the mechanism and control of porphyrin and corrin biosynthesis. Some preliminary results are discussed.

Intermolecular tritium transfer in the transcarboxylase reaction

Transfer of tritium from [3-3H]pyruvate into propionyl-CoA is found during the reaction of transcarboxylase: Methylmalonyl-CoA + pyruvate leads to oxalacetate + propionyl-CoA. About 5% of the tritium counts that are labilized in the reaction are found in a position of the propionate that exchanges rapidly with water in the presence of transcarboxylase. Transfer from [2-3H]propionate of propionyl-CoA to pyruvate is real but only about one-tenth as great. The tritium transfers between reactants on two subunits are difficult to explain by a "carbanion" mechanism of --C--H bond cleavage and support the cyclic mechanism in which carboxybiotin itself is the base and the enol form of biotin is the proton-transferring agent.

[On uroporphyrinogen formation: Studies with 1-aminomethyl-3, 8, 13, 18-tetra(2-carboxyethyl)-2, 7, 12, 17-tetracarboxymethylbilinogen (author's transl)]

The preparation of the aminomethyl-bilinogen which results from formal "head to tail" condensation of porphobilinogen is described. The chemical cyclocondensation of this compound at pH 7.4 yields uroporphyrinogen I. Enzymatic studies with enzyme preparations from Propionibacterium shermanii, which synthesize uroporphyrinogens from porphobilinogen, show that the rate of cyclisation is increased by these enzymes and indicate that the bilinogen also might be used for uroporphyrinogen III formation. This is also suggested by studies on the formation of cobyrinic acid from [4-14C]5-aminolevulinate via uroporphyrinogen III in the presence of the aminomethylbilinogen by cell-free extracts from Clostridium tetanomorphum.

Magnetic resonance studies of the proximity and spatial arrangement of propionyl coenzyme A and pyruvate on a biotin-metalloenzyme, transcarboxylase

A spin-labeled ester of CoA, R-CoA (3-carboxy-2,2,5,5-tetramethyl-1-pyrolidinyl-1-oxy CoA thioester), has been shown by competition studies using electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) to bind specifically to the propionyl-CoA binding sites of transcarboxylase. Titrations indicate 0.7 +/- 0.2 binding site for R-CoA per enzyme-bound biotin with a dissociation constant of 0.33 +/- 0.12 mM. Propionyl-CoA binds to this site with a 1.3-fold lower disonable agreement with kinetically determined inhibitor constants of CoA and propionyl-CoA and propionyl-CoA (D. B. Northrop (1969), J. Biol. Chem. 244, 5808). The bit of this spin-label on 1/T1 of water protons. The formation of a ternary transcarboxylase-R-CoA-pyruvate complex is suggested by the failure of pyruvate to displace R-CoA from the tight site and is established by the paramagnetic effects of enzyme-bound R-CoA on the relaxation rates of the protons and 13C atoms of enzyme-bound pyruvate. From the paramagnetic effects of R-CoA on the relaxation rates of the methyl protons of pyruvate at 40.5 and 100 MHz, and on the 13C-enriched carbonyl and carboxyl carbon atoms of pyruvate at 25.1 MHz, a correlation time of 7 nsec and distances from the bound nitroxide radical to the methyl protons, the carbonyl, and carboxyl carbon atoms of bound pyruvate of 7.9 +/- 0.7, 10.3 +/- 0.8, and 12.1 +/- 0.9 A, respectively, are calculated. These distances establish the close proximity of the CoA ester and keto acid sites on transcarboxylase. Together with the previously determined distances from the enzyme-bound (Co(II) to the methyl protons and 2 carbon atoms of bound pyruvate and to 12 protons and 3 phosphorus atoms of bound propionyl-CoA, the present distances are used to derive a composite model of the bound substrates in the overall transcarboxylation reaction. In this model the distance from the methyl carbon of pyruvate and the methylene carbon of propionyl-CoA, between which the carboxyl transfer takes place is only approximately 7 A. Depending on the detailed mechanism of the carboxyl transfer, the distance through which the carboxybiotin must migrate is therefore between 0 and 7 A. Hence the major role of the 14-A arm of carboxybiotin is not to permit a large carboxyl migration but, rather to permit carboxybiotin to traverse the gap which occurs at the interface of three subunits and to insinuate itself between the CoA and keto acid sites.

1H and 31P Fourier transform magnetic resonance studies of the conformation of enzyme-bound propionyl coenzyme A on the transcarboxylase

The relaxation rates of the carbon-bound protons and of the three assigned phosphorus resonances of propionyl-CoA were measured in solutions of free propionyl-CoA and of the transcarboxylase-propionyl-CoA complex. In free propionyl-CoA, analysis of the 1/T1 values of 15 protons at 100 and 220 MHz and of 1/T1 and 1/T2 of the three phosphorus atoms at 40.5 MHz indicated free rotation of the propionyl region (taur approximately 3 x 10(-11) sec) but hindered motion of the remainder of the molecule with correlation times of 1-3. 5 x 10(-10) sec, approaching the tumbling time of the entire molecule (taur - 6 x 10(-10) sec. The correlation times of the three phosphorus atoms were indistinguishable from those of their nearest neighbor protons. The effects of three homogeneous enzyme preparations with varying contents of Zn(II), Co(II), and Cu(II) on 1/T1 of 12 protons and 3 phosphorus atoms of prionyl-CoA were analyzed with the help of simultaneous equations to yield the individual contributions at the three metal sites. Only diamagnetic effects were detected on the relaxation rates of the three phosphorus atoms. From the diamagnetic effects it was calculated that the motions of the prionyl side chain and of the terminal pantetheine methylene protons were hindered on the enzyme by an order of magnitude (taur approximately 6 x 10(-10) sec) and that the phosphorus atoms were hindered by two orders of magnitude (taur approximately 1 x 10(-8) sec) over the taur values found in free propionyl-CoA, but that these taur values remained well below that of the entire protein molecule (taur =6 x 10(-7) sec)...

Isolation and characterization of a pyrophosphate-dependent phosphofructokinase from Propionibacterium shermanii

A pyrophosphate-dependent phosphofructokinase (pyrophosphate; D-fructose-6-phosphate-1-phosphotransferase) has been purified and characterized from extracts of Propionibacterium shermanii. The enzyme catalyzes the transfer of phosphate from pyrophosphate to fructose 6-phosphate to yield fructose-1,6-P2 and phosphate. This unique enzymatic activity was observed initially in Entamoeba histolytica (Reeves, R.E., South, D.J., Blytt, H.G., and Warren, L. G. (1974) J. Biol. Chem. 249, 7734-7741). This is the third pyrophosphate-utilizing enzyme that these two diverse organisms have in common. The others are phosphoenolpyruvate carboxytransphosphorylase and pyruvate phosphate dikinase. The PPi-phosphofructokinase from P. shermanii is specific for fructose-6-P and fructose-1,6-P2, no other phosphorylated sugars were utilized. Phosphate could be replaced by arsenate. The Km values are: phosphate, 6.0 X 10(-4) M; fructose-1, 6-P2, 5.1 X 10(-5) M; pyrophosphate, 6.9 X 10(-5) M; and fructose-6-P, 1.0 X 10(-4) M. The S20w is 5.1 S. The molecular weight of the native enzyme is 95,000. Sodium dodecyl sulfate electrophoresis of the enzyme showed a single band migrating with an Rf corresponding to a molecular weight of 48,000. Extracts of P. shermanii have PPi-phosphofructokinase activity approximately 6 times greater than ATP-phosphofructokinase and 15 to 20 times greater than fructose diphosphatase activities. It is proposed that (a) PPi may replace ATP in the formation of fructose-1-6-P2 when the organism is grown on glucose and (b) when the organism is grown on lactate or glycerol the conversion of fructose-1,6-P2 to fructose-6-P during gluconeogenesis may occur by phosphorolysis rather than hydrolysis.

[Ribonucleotide reductase in Propionibacterium shermani]

The cell-free extract of Propionibacterium shermanii was found to contain B12-dependent ribonucleotide reductase. The extract of the cells grown under the conditions of the inhibited synthesis of vitamin B12 reduces ribonucleotides with the participation of B12-independent enzyme. The synthesis of B12-dependent apoenzyme of ribonucleotide reductase is partially maintained under these conditions. Both enzymes reduce preferably ribonucleoside diphosphates. The reducing agent of nucleotides in vitro is lipoic acid or dithiothreitol, in the B12-dependent pathway, and NADPH and thioredoxin, in the B12-independent pathway. Only B12-independent ribonucleotide reductase requires Mg2+ ions. Vitamin B12 in the coenzyme form inhibits the activity of B12-independent enzyme.

Stereochemistry of propionyl-coenzyme A and pyruvate carboxylations catalyzed by transcarboxylase

The stereochemistry of the two half-reactions catalyzed by the biotin-containing enzyme, transcarboxy-lase from Propionobacteria shermanii, has been determined. The pro-R hydrogen at C-2 of propionyl-coenzyme A is replaced by CO2 in formation of the S isomer of methylmalonyl-CoA, defining the process as retention of configuration. This C-2 hydrogen is abstracted at a rate identical with product formation. For the other half-reaction, pyruvate to oxalacetate, the chiral methyl group methodology of Rose (I. A. Rose (1970), J. Biol. Chem. 245, 6052) was employed. First, it was determined with [3-2-He]pyruvate that a kinetic deuterium isotope effect of 2.1 occurs at Vmax in this carboxyl transfer, indicating that the necessary requirement for discrimination against heavy isotopes of hydrogen existed. Then, 3(S)-[3-2-H,3-H]pyruvate, generated from 3(S)-]E-2-H,3-H]phosphoglycerate, was carboxylated and the oxalacetate trapped as [3030H]malate using malate dehydrogenase. Exhaustive incubation of the tritiated malate (3-H/14-C = 1.95) with fumarase to labilize the pro-R hydrogen at C-3 resulted in release of 65% of the tritium into water. Reisolation of the malate after fumarase action yielded a 30H/14-C ration of 0.67, indicating 34% retention as expected. The theoretical enantiotopic distribution for the observed k1H/k2H of 2.1 is 68:32. Selective enrichment of tritium in the pro-R position at C-3 of malate indicates enzymatic carboxylation of pyruvate with retention of configuration in this half-reaction also.

Evaluation of human oral organisms and pathogenic Streptococcus for production of IgA protease

IgA protease is a proteolytic enzyme found in whole human saliva and in dental plaque that cleaves both secretory and myeloma IgA of human origin to yield intact Fabalpha and Fcalpha fragments. To determine which bacteria are capable of producing this enzyme, we have examined a variety of strains normally found in the human oral cavity and a number of streptococci of known Lancefield group serotype. Streptococci of groups A, B, C, D, F, G, H, M, and N, Streptococcus mutans, Streptococcus sanguis, Streptococcus mitior, Streptococcus salivarius, Streptococcus faecalis, Veillonella, Lactobacillus, Actinomyces, Propionibacterium, Bacteroides, and Fusobacterium were grown in liquid medium, and fluids were examined for IgA protease activity. Only S. sanguis and clinically isolated group H streptococci elaborated IgA protease under the culture conditions used. Negative strains could not be stimulated to produce the enzyme when cultured in the presence of secretory IgA. Among the natural oral bacteria, capacity to produce IgA protease is restricted to certain species of Streptococcus, notably those of the group H serotype. Since secretory immunity is mediated by the IgA class of antibody, the presence of this enzyme at mucosal surfaces could modify the secretory immune function.

Isolation of peptides from the carboxyl carrier subunit of transcarboxylase. Role of the non-biotinyl peptide in assembly

Transcarboxylase is made up of a central hexameric subunit (S20,W similar 12 S), three peripheral dimeric metallo subunits (S20,W similar to 5 S), and six biotinyl carboxyl carrier subunits (S20,W similar to 1.3 S). The results presented here show that the carboxyl carrier subunit is required for assembly of the 12S and 5S subunits into the oligomer. However, only a portion of the subunit is required for assembly. On treatment of transcarboxylase briefly with trypsin at pH 6.3 extremely susceptible peptide bonds of the carboxyl carrier protein are cleaved releasing biotinyl peptides of about similar to 66 and similar to 40 residues. The resulting trypsinized transcarboxylase, though enzymatically inactive, remains essentially intact as judged by its hydrodynamic and molecular sieving properties. The modified enzyme can be dissociated at pH 8 to the central 12S subunit and peripheral 5S subunit to which the residual portion(s) of the cleaved carboxyl carrier protein is still attached. These components can then be separated by molecular sieving. The residual portion of the carboxyl carrier protein (non-biotinyl peptide) can then be isolated by dissociation of the 5S subunit complex at pH 9 and by chromatography over Bio-Gel A-1.5m. The isolated non-biotinyl peptide has been shown to contain the combining domain of the 1.3SE carboxyl carrier protein since it causes combination of the 12S and 5S subunits. Active enzyme is formed by combination of the intact carboxyl carrier protein and the 12S and 5S subunits and an inactive oligomer of similar size is formed if the non-biotinyl peptide is used in place of the carboxyl carrier protein. The similar to 66- and similar to 40-residue biotinyl peptides, which are released by the trypsin treatment, apparently occur on an exposed portion of the enzyme. This portion of the carboxyl carrier protein apparently serves to place the biotinyl group adjacent to the two substrate sites of the enzyme, one of which is on the peripheral subunit and the other on the central subunit. Thus the carboxyl carrier protein has two functions: one portion holds the 12S and 5S subunits in juxtaposition and the other portion orients the biotinyl group adjacent to the substrate sites so that it may function as a carboxyl carrier between the sites.

Evidence that the two partial reactions of transcarboxylation are catalyzed by two dissimilar subunits of transcarboxylase

The results presented here show that isolated subunits of transcarboxylase specifically catalyze the two partial reactions of transcarboxylation as shown in eq 1-3. The 12S central subunit is active in the transcarboxylation with methylmalonyl-CoA but inactive with oxalacetate and the peripheral metallo 5S subunit is active in the transcarboxylation with oxalacetate but inactive with methylmalonyl-CoA. These subunits, likewise, are specific for the reverse partial reactions; the central subunit catalyzing transfer from the carboxylated biotinyl group to propionyl-CoA to yield methylmalonyl-CoA and the peripheral subunit to pyruvate to yield oxalacetate. Thus, the central subunit contains the sites for the CoA esters (methylmalonyl-CoA and propionyl-CoA) and the peripheral metallo subunits for the keto acids (oxalacetate and pyruvate). In the overall reaction the biotinyl carboxyl carrier protein acts as a shuttle to carry the carboxyl groups between the two subunits. Biotin and certain biotin analogs are inactive in these partial reactions but the similar to 40- or similar to 66-residue biotinyl peptides, which are derived from the carboxyl carrier protein, are active. Transcarboxylase can be reconstituted from its isolated subunits and a comparison was made of the rate of the overall reaction when the subunits were assembled, as in the intact enzyme, with that obtained when the reaction was catalyzed by the nonassembled subunits. In the latter case, since the biotinyl carboxyl carrier subunit must diffuse from one subunit to the other, the overall reaction is much slower than with the assembled subunits. The reaction with trypsinized transcarboxylase from which the similar to 66-residue and similar to 40-residue biotinyl peptides have been stripped, likewise, was slow even though the biotinyl peptides were added to the reconstitution mixture. The 12SH and 5SE subunits remain assembled after trypsin treatment but the biotinyl peptides apparently do not combine firmly or properly with the trypsinized enzyme and the biotinyl group apparently must oscillate as a carboxyl carrier between the two sites on the subunits by diffusion.

Purification of the subunits of transcarboxylase by affinity chromatography on avidin-sepharose

Transcarboxylase consists of a central 12 SH subunits each of which is linked to the central subunit by two similar to 1.3 SE biotin carboxyl carrier proteins. The subunits from dissociated transcarboxylase have been difficult to isolate because conditions which stabilize them also promote their reassociation to the intact enzyme. In this paper, we describe the use of avidin-Sepharose to adsorb the enzyme from crude extracts or partially purified transcarboxylase of propionibacteria. After removing impurities by washing the column with phosphate buffer at pH 6.5, in which the transcarboxylase is stable, the enzyme is dissociated first by elution at pH 8 yielding a fraction containing mostly 12 SH subunit which can be rapidly stabilized against dissociation to 6 SH without the problem of reconstitution because the 1.3 SE and most of the 5 SE subunits are not eluted. The second elution is at pH 9 which yields the 5 SE subunit by dissociation from the 1.3 SE biotin subunit and the 1.3 SE subunit remains bound to the avidin. The 12 SH and 5 SE subunits are further purified by glycerol density gradient centrifugation or by chromatography on Bio-Gel. Very active enzyme can be reconstituted from these subunits upon the addition of the 1.3 SE subunit.

Beta-galactosidase of Propionibacterium shermanii

Ten strains of Propionibacterium shermanii were tested for beta-galactosidase (beta-gal) activity. Of these ten strains, five yielded enhanced enzyme activity when cell suspensions were treated with toluene-acetone; on solvent treatment, the remaining five lost a considerable portion of the activity found in whole-cell suspensions. By using a strain yielding decreased activity upon solvent treatment, explanations for the loss in activity were sought through assays for possible alternative beta-galactoside utilization mechanisms. When this strain was assayed for beta-D-phosphogalactoside galactohydrolase by using orthonitrophenyl-beta-D-galactopyranoside-6-P04 as a substrate, the activity was wither lower or indiffernt as compared with beta-gal activity determined simultaneously. Cell suspensions of P. shermanii 7 and 22 (strains chosen for further work) grown separately on the individual substrates (lactose, glucose, galactose, and sodium lactate) did not show significant differences in beta-gal activity. Optimal temperature for beta-gal activity in untreated and toluene-acetone-treated cell suspensions of strain 7 was 52 C. With strain 22, of the temperatures tested, maximal activity in untreated cell suspensions was noted at 58 C and with solvent-treated cells at 32 C. In the cell-free extract (CFE) system, both strains exhibited maximal activity at 52 C. Optimal pH for untreated and solvent-treated cell suspensions of both strains was around 7.5. In the P. shermanii 22 CFE system, maximal activity occurred at pH 7.0; pH had very little effect on enzyme activity in P. shermanii 7 CFE. Sodium or potassium phosphate buffers in the assay system yielded the best activity. In the CFE system of these two strains, Mn2+ was definitely stimulatory, but in untreated and solvent-treated cell systems of these strains presence or absence of Mn2+ in the assay system had variable effects on enzyme activity. Maximal beta-gal activity was noted in P. shermanii 7 cells harvested after 28 h of growth at 32 C in sodium lactate broth. Sulfhydryl-group blocking agents inhibited enzyme activity in P. shermanii 22 CFE; the inhibition was partly reversed by dithiothreitol.

Phosphatase activity of anaerobic organisms

Anaerobic organisms were tested for phosphatase activity in different pH ranges. Several groups of organisms displayed characteristic patterns. Bacteroides fragilis, B. melaninogenicus, and B. ruminicola produced phosphatase with strongest activity at pH 8.6. Fusobacterium mortiferum was the only species of this genus to show strong hydrolysis. The enzyme was active in both acid and alkaline ranges. The activity of gram-positive organisms was variable, the most active groups being Clostridium perfringens, Peptostreptococcus intermedius, P. micros, and Peptococcus constellatus. The incorporation of phosphatase activity into the identification scheme of anaerobes seems feasible. There was a correlation of hydrolysis with several important pathogens.