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Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 1,225 records · Page 68Linked to original sources
PubMed1981

Studies on proteinases from the digestive organs of sardine. I. Purification and characterization of three alkaline proteinases from the pyloric caeca.

Three alkaline proteinases designated I, II and III are found in the pyloric caeca of sardine and isolated by (NH4)2SO4 fractionation, DEAE-cellulose chromatography and gel filtration on Sephadex G-100. The final preparations were judged homogeneous by multiple criteria. The molecular weights of the enzymes I, II and III were determined by the sedimentation equilibrium method to be 22 900, 28 700 and 27 000, respectively. The isoelectric points were 5.45, 5.30 and 4.85, and the sedimentation coefficients (S0 20, w) were 2.91, 3.06 and 2.94, respectively. Enzymes II and III had similar amino acid compositions which were different from that of enzyme I, especially in the content of lysine, valine and tyrosine. All the enzymes belonged to a group of serine proteases. Enzymes II and III were found to be an anionic alpha-chymotrypsin-like enzymme and an anionic trypsin-like enzyme, respectively. Although these fish enzymes had properties in common with those of bovine pancreatic cationic trypsin and chymotrypsin, they are distinctly different in their optimum pH, pH stability, net charge and immunological properties.

Amino Acids↗
PubMed1981

Studies on proteinases from the digestive organs of sardine. II. Purification and characterization of two acid proteinases from the stomach.

Two fish acid proteinases designated acid proteinase I and II were found and isolated by (NH4)2SO4 fractionation, CM-cellulose chromatography and gel filtration on Sephadex G-100. The final preparations were judged nearly homogeneous by multiple criteria. The molecular criteria. The molecular weights of the enzymes I and II were determined by the sedimentation equilibrium method to be 37 000 and 33 400, respectively. The sedimentation coefficients (S0 20, w) were 3.06 and 3.09, respectively. Enzymes I and II contained similar amino acid composition except for the contents of histidine, arginine, threonine, serine and proline. Enzymes I and II differed from each other in optimal pH and stability at pH 7. Each enzyme could scarcely hydrolyze a synthetic pepsin substrate, N-acetyl-L-phenylalanyl-3,5-diiodo-L-tyrosine (APDT). Both of the enzymes were inhibited by acid proteinase specific reagents: pepstatin, diazoacetyl-DL-norleucine methyl ester (DAN), 1,2-epoxy-3-(p-nitrophenoxy) propane (EPNP) and p-bromophenacyl bromide. These results indicate fish enzymes are similar to mammalian pepsin and microbial acid proteinases in their active site structure having two different carboxyl groups, although they differ in regard to a number of molecular and enzymatic properties.

Amino Acids↗
PubMed1981

The effect of spermine on the interaction of AMP deaminase with threonine dehydratase activity in yeast.

Evidence suggesting that AMP deaminase (EC 3.5.4.6) is responsible for the stimulation of threonine dehydratase (EC 4.2.1.16) activity in situ is presented using yeast cells which have been rendered permeable. The addition of polyamine, an activator of AMP deaminase, resulted in the increase in ammonia concentration, which can stimulate the activity of yeast threonine dehydratase. Polyamine may regulate the synthesis of isoleucine and valine, and of the intermediates of citric acid cycle through the activation of AMP deaminase-threonine dehydratase system as a 'cascade system' in yeast.

AMP Deaminase↗
PubMed1981

In situ studies on AMP deaminase as a control system of the adenylate energy charge in yeasts.

The role of AMP deaminase reaction in the stabilization of the adenylate energy charge was investigated using permeabilized yeast cells. The addition of Pi or Zn2+, which inhibits AMP deaminase, remarkably retarded the depletion of total adenylate pool and the recovery of the adenylate energy charge. Polyamine, an activator of the enzyme, decreased total adenylates, resulting in the enhanced recovery of the energy charge in situ. AMP deaminase can act as a regulatory enzyme in the system that stabilizes the adenylate energy charge in yeast cells under the conditions of severe metabolic stress.

AMP Deaminase↗
PubMed1981

1-Oxacephalosporins: enhancement of beta-lactam reactivity and antibacterial activity.

The effect of replacement of sulfur in the cephem nucleus by oxygen upon the beta-lactamase stability, infrared carbonyl frequency of the beta-lactam ring, and antibacterial activity was investigated. The replacement reduced the stability of beta-lactam compounds to beta-lactamases, increased the IR frequencies, and enhanced the intrinsic antibacterial activity against bacterial strains without beta-lactamase. The instability of 1-oxacephalosporins to beta-lactamases, in other words, high reactivity to the enzymes, seemed to be due to the enhanced chemical reactivity of their beta-lactam rings which was indicated by their higher IR beta-lactam carbonyl frequencies. Based on a view that acylation of the enzyme by beta-lactam compounds occurred in both cases of beta-lactamase hydrolysis and target enzyme inhibition, the suggestion was made that one of the factors which conferred the higher intrinsic antibacterial activity on 1-oxacephalosporins was their high reactivity to the target enzyme(s), as was the case with beta-lactamases.

Anti-Bacterial Agents↗
PubMed1981

Purification and characterization or porcine kidney cathepsin B.

Three types of cathepsin B were purified from porcine kidney by a procedure involving ammonium sulfate fractionation, acetone fractionation, pH-gradient elution from CM-cellulose, gel filtration, salt gradient elution chromatography of CM-cellulose and finally preparative isoelectric focusing. The isoelectric points for the three types of cathepsin B were at pH 5.5 (Type I), pH 5.9 (Type II), and pH 6.2 (Type III). The molecular weights were estimated at 24,000 (Types I and II), and 29,000 (Type III) by SDS-polyacrylamide gel electrophoresis. The preparations were all unstable above pH 7.0 when compared with the stability at their optimal pH of around pH 6.0. The isozymes cleaved benzyloxycarbonyl-phenylalanyl-arginine-4-methyl-7-coumarylamide at pH 6.0 and at 40 degrees C with Km values of 0.225 mM (Types I and III) and 0.204 mM (Type II) and with kcat values of 71 s-1 (Types I and II) and 63 s-1 (Type III). They were strongly inhibited by iodoacetate, leupeptin and antipain, but not by DFP, PMSF, or pepstatin. The values of apparent inhibition constant for leupeptin were 15 nM (Types I and II) and 17 nM (Type III).

Animals↗
PubMed1981

Effect of age on active and inactive plasma renin in normal subjects and in patients with essential hypertension.

The effect of age on the levels of active and trypsin-activatable inactive plasma renin was examined in 41 normal subjects and 54 patients with essential hypertension, during recumbency and after stimulation with furosemide and ambulation. Active renin levels in supine subjects and patients decreased with age. Inactive renin levels did not change with age in normal subjects, whereas in hypertensive patients they decreased with age. Following stimulation with furosemide and ambulation, the levels of active renin increased but the responsiveness to stimulus decreased with age in both groups. In contrast, inactive renin levels slightly increased after furosemide administration and ambulation, resulting in increased proportion of active to total renin. These data show that an acute stimulation with furosemide and ambulation affects mainly the active form of plasma renin, and the effect of age on inactive plasma renin in normal subjects may be different from that in patients with essential hypertension.

Adult↗
PubMed1981

Role of the 7 alpha-methoxy and side-chain carboxyl of moxalactam in beta-lactamase stability and antibacterial activity.

The effects of the alpha-carboxyl of the phenylmalonyl side chain and the 7 alpha-methoxy group in moxalactam (6059-S) (7 beta-[2-carboxy-2-(4-hydroxyphenyl) acetamido]-7 alpha-methoxy-3[[(1-methyl-1H-tetrazol-5-y])thio] methyl]-1-oxa-1-dethia-3-cephem-4-carboxylic acid) and in the 1-sulfur congener on the stability to beta-lactamase were investigated by spectrophotometric and microbiological assays. The 7 alpha-methoxy substituent stabilized the compounds against penicillinase hydrolysis, and the alpha-carboxyl group stabilized them against cephalosporinase. An exception is the beta-lactamase produced by Proteus vulgaris, an inducible cephalosporinase, which hydrolyzed compounds having the alpha-carboxyl group but not those having the 7 alpha-methoxy group. Both substituents exerted their stabilizing effects independently, and compounds with both substituents, e.g., moxalactam (6059-S) and its 1-sulfur congener, were resistant to both penicillinases and cephalosporinases. The stabilization of the compounds to beta-lactamase hydrolysis improved their antibacterial activity against beta-lactamase-producing strains.

Anti-Bacterial Agents↗
PubMed1981

Penetration of moxalactam into its target proteins in Escherichia coli K-12: comparison of a highly moxalactam resistant mutant with its parent strain.

An eschericia coli K-12 mutant highly resistant to moxalactam but only slightly resistant to other beta-lactam antibiotics was obtained by mutagen treatment. The affinity of moxalactam for its target penicillin-binding proteins was unchanged, as was the level of beta-lactamase activity. The penetration of [14C] moxalactam, however, was markedly reduced in the mutant. Electrophoretic analysis revealed alterations of the outer membrane proteins. A reduction in the amount of one of the pore-forming proteins (porins) was especially noteworthy. These data suggest that moxalactam resistance is the result of an alteration in the outer membrane structure.

Bacterial Proteins↗
PubMed1981

A rapid and large-scale isolation of renin from mouse submaxillary gland by pepstatin-aminohexyl-agarose affinity chromatography.

A pressor enzyme, renin, was purified about 60-fold by chromatography on an affinity column including pepstatin-aminohexyl-agarose with a high yield of 83% from the homogenate of adult mouse submaxillary glands. The renin obtained by the one-step purification was electrophoretically homogenous on SDS-polyacrylamide gel and was as active as an absolutely pure renin. The renin purified by the affinity column could be separated into five active components by chromatography on CM-cellulose. Each of these renins gave a symmetrical elution profile on the CM-cellulose column and a discrete protein band on polyacrylamide gel electrophoresis at pH 8.6. Administration of nanogram quantities of each of the two major renin fractions to nephrectomized rats caused a sustained rise of blood pressure and decrease in sensitivity of the animal to angiotensin II. This rapid and large-scale purification method using pepstatin-aminohexyl-agarose eliminates all four fractionation steps reported previously for the isolation of mouse submaxillary gland renin.

Animals↗