Bifunctionality and pseudoisozymes of pyruvate kinase from codfish muscle

Pyruvate kinase has been purified from codfish muscle. The ratio of phosphotransferase and oxalacetate decarboxylase activities remains relatively constant throughout purification steps. These two activities are dependent as well as sensitive to sulfhydryl reagents. In the presence of dithioerythritol, only one molecular form of pyruvate kinase is detected. However, the enzyme exists as four pseudoisozymes in the presence of 2-mercaptoethanol. The pseudoisozymes of codfish pyruvate kinase are interconvertible under the influence of sulfhydryl reagents.     

Properties and characterization of a highly purified sarcoplasmic reticulum Ca2+-ATPase from dog cardiac and rabbit skeletal muscle

Sarcoplasmic reticulum (SR) Ca2+-ATPase was purified from dog cardiac and rabbit skeletal muscle using Triton X-100 at optimal ratios of 0.5 for cardiac and 0.5 to 1.0 for skeletal SR. The yields of Ca2+-ATPase were 4 to 5 and 1 to 2.2 mg/100 mg of cardiac and skeletal SR protein, respectively. The enzyme activities were 547 +/- 67 mumol ADP/mg/h for cardiac and 1192 +/- 172 mumol ADP/mg/h for skeletal Ca2+-ATPase. Removal of excess Triton X-100 increased the enzyme activities to 719 +/- 70 and 1473 +/- 206 mumol ADP/mg/h, respectively. The residual content of Triton X-100 for cardiac and skeletal Ca2+-ATPase was 20 and 5 mol/mol of enzyme, respectively. Maximum levels of phosphoenzyme were 4.4 +/- 0.2 and 5.6 +/- 0.6 nmol/mg in each case. A single protein band of 100 kDa was obtained for each purified Ca2+-ATPase by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The preparations were stable at -80 degrees C for 5 months in the presence of 1 mM Ca2+. The phospholipid content of the purified enzyme was 2-fold greater than that of native cardiac and skeletal SR microsomes. Repeated washing of the purified enzyme preparation did not alter the phospholipid content or the specific activities.     

Phosphate-limited culture of Azotobacter vinelandii.

Batch cultures of Azotobacter vinelandii grown in phosphate-deficient media were compared with control cultures grown in phosphate-sufficient media. Phosphate limitation was assessed by total cell yield and by growth kinetics. Although cell protein, nucleic acids, and early growth rate were unaffected by phosphate deficiency, cell wall structure, oxygen uptake, and cell viability were significantly affected. Also, phosphate-limited cells contained much larger amounts of poly-beta-hydroxybutyric acid but lower adenylate nucleotide energy charge than did control cells. The ratio of adenosine 5'-triphosphate to adenosine 5'-diphosphate was much lower in phosphate-deficient cells. The data indicate a substrate saving choice of three metabolic pathways available to this organism under different growth conditions.     

Esterase activity of liver alcohol dehydrogenase.

Liver alcohol dehydrogenase is found to possess, in addition to its dehydrogenase and dismutase activities, the ability to hydrolyze octanoate esters at a rate approximately $\text{1}\text{500}\text{–}\text{1}\text{1000}$ of that of the dehydrogenase reaction. The esterase and dehydrogenase activities exhibit an identical isozyme pattern indicating that the same protein catalyzes both reactions. Inhibition studies suggest that the esterase activity presumably shares the catalytic domain with the dehydrogenase activity.     

Routes to higher-carbon sugar derivatives having keto-acetylenic and -alkenic,and α,β-unsaturated aldehyde functionality

Oxidative dimerization of 7,8-dideoxy-1,2:3,4-di-O-isopropylidene-d-glycero-α-d-galacto-oct-7-ynopyranoside (1) gave a high yield of the diyne 2, readily reduced by lithium aluminum hydride to the trans,trans-diene (4). The structures of 2 and 4 were established spectroscopically and by degradation of 4 to d-glycero-d-galacto-heptitol (perscitol). A mixture of the alkyne 1 and its 7-epimer 10 was readily oxidized by dimethyl sulfoxide-acetic anhydride to the 6-ketone 11, and the 8-alkene analog was similarly prepared from the alkenes derived from 1 and 10. Likewise, oxidation of 6,7-dideoxy-1,2-O-isopropylidene-α-d-gluco(and β-L-ido)-hept-6-enopyranose gave the corresponding 5-ketone. The acetylenic ketone 11 gave a crystalline oxime and (2,4-dinitrophenyl)hydrazone, the latter being accompanied by the product of attack of the reagent at the acetylene terminus (C-8). Previous work had shown that formyl-methylenetriphenylphosphorane did not convert 1,2:3,4-di-O-isopropylidene-6-aldehydo-α-d-galacto-hexodialdo-1,5-pyranose into the corresponding C₈ unsaturated aldehyde, although the latter was obtainable via1 and 10 by an ethynylation-hydroboration sequence. The Wittig route with formylmethylenetriphenylphosphorane is shown to be satisfactory for obtaining C₇ unsaturated aldehydes from 3-O-benzyl-1,2-O-isopropylidene-5-aldehydo-α-d-xylo-pentodialdo-1,4-furanose (22) and the 3-epimer of 22, respectively. These reactions provide convenient access to higher-carbon sugars and chiral dienes for synthesis of optically pure products of cyclo-addition reactions.     

Five structural classes of major outer membrane proteins in Neisseria meningitidis

Group B Neisseria meningitidis is thus far subdivided into 15 protein serotypes based on antigenically different major outer membrane proteins. Most serotypes have three or four major proteins in their outer membranes. Comparative structural analysis by chymotryptic 125I-peptide mapping was performed on these major proteins from the prototype strains as well as from six non-serotypable strains. The major outer membrane proteins from each of the serotypes were first separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis using the Laemmli system. Individual proteins within the gel slices were radioiodinated and digested with chymotrypsin, and then their 125I-peptides were separated by electrophoresis and chromatography on cellulose thin-layer plates. The peptide maps obtained by autoradiography were categorized into five different structural classes which correlated with the apparent molecular weights of proteins, i.e., 46 +/- 1K, 41 +/- 1K, 38 +/- 1K, 33 +/- 1K, and 28 +/- 1K. Each of the major outer membrane proteins within a strain had a distinctly different chymotryptic peptide map, indicating significant differences in the primary structure of these proteins. In contrast, outer membrane proteins of the same or very similar molecular weight from different serotype strains had similar, occasionally identical peptide maps, indicating a high degree of structural homology. The unique peptides from proteins of the same structural classes were often hydrophilic, whereas common peptides were often hydrophobic, suggesting that the serotype determinants reside within the variable hydrophilic regions of major outer membrane proteins.     

Influence of monovalent cations on the Ca2+-ATPase of sarcoplasmic reticulum isolated from rabbit skeletal and dog cardiac muscles. An interpretation of transient-state kinetic data

Transient-state kinetics of phosphorylation and dephosphorylation of the Ca2+-ATPase of sarcoplasmic reticulum vesicles from rabbit skeletal and dog cardiac muscles were studied in the presence of varying concentrations of monovalent and divalent cations. Monovalent cations affect the two types of sarcoplasmic reticulum differently. When the rabbit skeletal sarcoplasmic reticulum was Ca2+ deficient, preincubation with K+ (as compared with preincubation with choline chloride) did not affect initial phosphorylation at various concentrations of Ca2+, added with ATP to phosphorylate the enzyme. This is in contrast to preincubation with K+ of the Ca2+-deficient dog cardiac sarcoplasmic reticulum, which resulted in an increase in the phosphoenzyme level. When Ca2+ was bound to the rabbit skeletal sarcoplasmic reticulum, K+ inhibited E - P formation; but under the same conditions, E - P formation of dog cardiac sarcoplasmic reticulum was activated by K+ at 12 microM Ca2+ and inhibited at 0.33 and 1.3 microM Ca2+. Li+, Na+ and K+ also have different effects on E - P decomposition of skeletal and cardiac sarcoplasmic reticulum. The latter responded less to these cations than the former. Studies with ADP revealed differences between the two types of sarcoplasmic reticulum. For rabbit skeletal sarcoplasmic reticulum, 40% of the phosphoenzyme formed was 'ADP sensitive', and the decay of the remaining E - P was enhanced by K+ and ADP. Dog cardiac sarcoplasmic reticulum yielded about 40--48% ADP-sensitive E - P, but the decomposition rate of the remaining E - P was close to the rate measured in the absence of ADP. Thus, these studies showed certain qualitative differences in the transformation and decomposition of phosphoenzymes between skeletal and cardiac muscle which may have bearing on physiological differences between the two muscle types.     

Multiple forms of glucosephosphate isomerase in maize

Three apparently different glucosephosphate isomerases are found in the developing seeds of maize (Zea mays L.). Glucosephosphate isomerase I is found in both the endosperm and embryo. It is separable by column chromatography from glucosephosphate isomerase II of the developing endosperm and glucosephosphate isomerase III of the developing embryo and is further distinguished from them by heat stability, temperature activation, and relative insensitivity to the presence of zinc ions in the reaction mixture. Glucosephosphate isomerases II and III elute in the same fractions from diethylaminoethyl cellulose columns but are distinguished by electrophoretic mobility and reaction to the presence of adenosine 5′-triphosphate in the reaction mixture. All three isomerases give multiple banding patterns on electrophoresis. An extensive investigation of the conditions generating additional electrophoretic species and chromatographically separable minor activity peak (Ia) from glucosephosphate isomerase I has shown that these transformations are enhanced by dialysis, column chromatography, ammonium sulfate fractionation, and treatment with urea. The transformations are retarded by the presence of mercaptoethanol during these operations. We concluded that the multiple banding pattern seen on electrophoresis of glucosephosphate isomerase I prepared by certain procedures is artifactual. In germinating seeds of maize, glucosephosphate isomerases I and III are detectable, but II is not. It is possible that glucosephosphate isomerase II specifically catalyzes a step in starch biosynthesis.     

The proteins of the inner membrane of rat liver mitchondria

Abteilung MolekulareBiologie, Max-Planck-Institut Experimentelle Medizin, Gottingen, Germany