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Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 1,207 records · Page 67Linked to original sources
PubMed1982

Properties of renin-binding protein.

Hog renal renin-binding protein could bind homologous and non-homologous renin but could not bind human renal renin. Renin-binding protein was only detected in the kidney and pituitary in which renin is found in relatively high concentration. The renal binding protein had no interaction with renal acid proteases nor with extrarenal renins obtained from pituitary and submaxillary glands, indicating that the binding is specific for renal renin. Subcellular localization of the binding protein was studied using rat kidney by differential and density gradient centrifugation. Most renin-binding protein was recovered in the cytosol fraction and was not associated with sedimentable subcellular organelles. A renin-secreting tumor (Juxtaglomerular cell tumor) in human kidney produced not only renin but also renin-binding protein in a very large quantity.

Animals↗
PubMed1982

Asparenomycins A, B and C, new carbapenem antibiotics. V. Inhibition of beta-lactamases.

Asparenomycins (ASMs) A, B and C inhibited a wide range of beta-lactamases including both cephalosporinases and penicillinases usually at concentrations less than 3 microM. On studying the mechanism of inhibition of beta-lactamases produced by Gram-negative bacteria by ASM A it was concluded that ASM A inhibited the beta-lactamases by acylating the enzymes. This conclusion was reached from the following observations. i) The inhibition was progressive with time. ii) The inhibitor formed stable complexes with the enzyme. iii) Before completing inhibition of one molecule of the enzyme, 1.8 molecules of the inhibitor were hydrolyzed.

Anti-Bacterial Agents↗
PubMed1982

Changes of glandular kallikrein activity in human plasma following glucose ingestion.

We studied the changes of glandular kallikrein activity in plasma of nine normal female volunteers, aged 22.2 +/- 1.20 years (mean +/- SEM), following 75 g glucose ingestion along with those of immunoreactive insulin, C-peptide immunoreactivity, free fatty acid and blood glucose using our recently developed assay system for plasma glandular kallikrein activity. Glandular kallikrein activities decreased initially from mean baseline level and then returned to baseline level with the lapse of time after glucose load. Furthermore, in hyperinsulinemic group, mean glandular kallikrein activities at 120 min after glucose load revealed to be significantly higher than those of normoinsulinemic group. The findings suggest that active glandular kallikrein is consumed and utilized during glucose uptake at the peripheral tissues, and hyperinsulinemia brings about prolonged activation of kallikrein-kinin system.

Adult↗
PubMed1981

A 56,000-dalton renin-binding protein in hog kidney is an endogenous renin inhibitor.

Renin-binding protein (RBP) in hog kidney was characterized and identified as a renin inhibitor. The molecular weight (Mr) of rBP is 56,000 when estimated by gel filtration. Its isoelectric point is 4.9. Upon binding to renin, it forms a renin.RBP complex with Mr = 113,000 as revealed by sedimentation equilibrium using an air-driven ultracentrifuge (Airfuge). The renin.RBP complex, formed by incubating hog kidney extract at 37 degrees C, is inactive when assayed with little dilution. On extensive dilution, however, this complex dissociates and acquires renin activity. The equilibrium between renin and renin.RBP complex and the equilibration rate were also studied by high performance liquid chromatographic gel filtration. The equilibrium was shifted to the complex, suggesting that RBP is present in an excess of renin in the kidney. The complex was shown to dissociate during the gel filtration due to rapid equilibration. Therefore, the elution position of the complex varied depending on flow rates, thereby making it difficult to determine the Mr of the complex by gel filtration. The renin.RBP complex is unlikely to occur in the normal kidney because renin and RBP are localized in the granule and cytosol fractions, respectively. RBP may provide security against accidental rupture of renin granules under abnormal circumstances.

Animals↗
PubMed1981

Demonstration of the formation of renin and renin-binding protein complex using high-performance liquid chromatography.

A high-performance liquid chromatograph equipped with the newly developed gel, TSK G3000SW, was used to study the interaction between renin and renin-binding protein (RBP). Previously, the interaction could only be demonstrated after overnight gel chromatography in the presence of a non-physiological sulfhydryl reagent. However, this new high-speed gel chromatography provided a clear separation of renin and renin--RBP complex within 40 min. It also demonstrated that the renin--RBP complex was formed at 37 degrees C in the absence of sulfhydryl reagent. Theses results indicate that the binding protein may play an important role in blood pressure regulation.

Animals↗
PubMed1981

Purification and characterization of taurodeoxycholate 7 alpha-monooxygenase in rat liver.

Taurodeoxycholate 7 alpha-monooxygenase was purified from rat liver microsomes of phenobarbital-treated rats. The purification was carried out by solubilization of microsomes by cholate, fractionation with polyethylene glycol, affinity chromatography, and hydroxylapatite chromatography. The purified preparation gave a single major band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and contained 13.5 nmol of cytochrome P-450/mg of protein, which corresponded to 6.8-fold purification from microsomes on the basis of specific heme content. The specific activity of the enzyme expressed by the enzyme activity per mg of enzyme protein was increased 72-fold from microsomes. The molecular weight of the enzyme was estimated to be 54,000 from calibrated polyacrylamide gel electrophoresis. The enzyme activity-pH curve gave a broad peak between pH 7.0 and 7.5. The Michaelis constant for taurodeoxycholate of the enzyme was 33 microM. Absorption spectra of the oxidized form of the enzyme showed a Soret band at 518 nm, typical of the low spin state of cytochrome P-450 and alpha and beta band at 571 and 534 nm, respectively. The CO-difference spectrum of the reduced enzyme showed a band at 450 nm characteristic of cytochrome P-450. Taurodeoxycholate 7 alpha-monooxygenase was reconstituted from the purified enzyme, NADPH-cytochrome P-450 reductase, dilauroylglyceryl-3-phosphorylcholine, and NADPH. The purified enzyme was free from steroid 12 alpha-hydroxylase, 25-hydroxylase, and 26-hydroxylase activities. The enzyme activity was seriously inhibited by nonionic detergents, but ot by aminoglutethimide or by metapyrone.

Animals↗
PubMed1981

In vitro and in situ studies on the inhibition of yeast AMP deaminase by fatty acids.

The effect of various fatty acids on the purified and in situ AMP deaminase (AMP aminohydrolase, EC 3.5.4.6) was investigated: both the purified AMP deaminase and the permeabilized system of yeast cells were used as the enzyme sources. (1) All the saturated fatty acids, longer than 10 in the hydrocarbon chain, were inhibitors of the purified enzyme in the absence of ATP, whereas no or little inhibition of the enzyme was observed in the presence of ATP. Unsaturated fatty acids acted as more potent inhibitors of the purified enzyme, although the addition of ATP increased the I0.5 values for these fatty acids. Fatty acids acted as non-competitive inhibitors without alteration of the affinity for the substrate in the absence and presence of ATP. (2) Unsaturated fatty acids showed a powerful inhibition of the in situ AMP deaminase, and the presence of ATP could scarcely affect the inhibition of the in situ enzyme by these fatty acids. On the other hand, no or little inhibition of the in situ enzyme by saturated fatty acids was observed in the absence and presence of ATP. The difference in the kinetics properties between the in situ and the purified enzyme suggests that there is difference in protein interactions for AMP deaminase in situ and in vitro.

AMP Deaminase↗