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N Nakai

Publications and source records attributed to N Nakai.

71 records · Page 4Linked to original sources
PubMed1984

Amino acid sequence around a cysteine residue in the active center of jack bean urease.

Cysteine residues in the active center of jack bean urease [EC 3.5.1.5] were modified with 14C-labeled diazonium-1H-tetrazole (DHT). The labeled enzyme was carboxymethylated with iodoacetic acid, and then hydrolyzed with trypsin. The tryptic digest was subjected to gel filtration on Sephadex G-50, yielding two radioactive fractions. The [14C]DHT-labeled peptide having a lower molecular weight, which was determined to be approximately 1,000 by the method of gel filtration, was further purified to homogeneity by ion-exchange chromatography on DEAE-Sephadex A-25. [14C]DHT-labeled cysteine was identified as cysteic acid after performic acid oxidation, and the amino acid sequence of the low-molecular-weight [14C]DHT-labeled peptide was determined to be Phe-Glu-Pro-Gly-Asp-Cys-Asn-Ser-Thr-Phe-Lys.

Amino Acid Sequence↗
PubMed1983

Effect of fructose 1,6-bisphosphate on the activity of liver pyruvate kinase after limited proteolysis with cathepsin B.

Treatment of rat liver-type pyruvate kinase with rabbit liver cathepsin B at pH 7.0 caused loss of activity in the standard assay with 0.6 mM of phosphoenolpyruvate. The modified enzyme exhibited about 10% of the original activity when assayed with 2.0 mM of the substrate. No detectable change in the subunit molecular weight of the enzyme occurred during inactivation. On addition of 4 microM fructose 1,6-bisphosphate the activity of the treated enzyme was restored to that of the original enzyme. Limited proteolysis of the enzyme by cathepsin B appears to enhance the requirement for the positive effector, fructose 1,6-bisphosphate.

Animals↗
PubMed1974

Amino acid sequence of rabbit muscle aldolase and the structure of the active center.

Elucidation of the amino acid sequence of fructose-1,6-bis-phosphate aldolase from rabbit muscle has made it possible to assign the positions of the functional groups known to play specific roles in the catalytic activity, and also to locate the buried, exposed, and active site cysteine residues. The results indicate that the middle portion of the polypeptide chain, including Cys-134, Cys-149, Cys-177, and Cys-l99, is buried in the native structure, with regions containing Cys-72, Lys-107, Lys-227, Cys-336, His-359, and the COOH-terminal residue (Tyr-361) folded into the active center of the enzyme, at or near the surface of the enzyme molecule.

Amino Acid Sequence↗
PubMedDate not supplied

Stable preparation of aldose reductase isoenzymes from human placenta.

An efficient, large-scale purification has been achieved for two aldose reductase isoenzymes from human placenta in stable form. The procedure included ammonium sulfate fractionation (45-75%), followed by chromatographies on Matrex Red A, DE-52 cellulose, and Matrex Orange A. The preparations were stable for at least 3 months at 3 degrees C. IC50 values toward sorbinil were similar to those reported for crude or partially purified enzymes, indicating that they retained native structures during the purification steps. The molecular weights of purified GAR1 and GAR2, named according to their order of elution with a salt gradient from a Matrex Red A column, were 36,600 and 40,300, respectively. Kinetic studies indicate that GAR1 belongs to an aldose reductase (a low-Km form) and GAR2 to an aldehyde reductase (a high-Km form). GAR2, an aldehyde reductase, was also active in the reduction of D-glucose, with an apparent Km comparable to that of GAR1 but with a Vmax only 14% that of GAR1.

Aldehyde Reductase↗