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Biomedical subjects

F Schneider

Publications and source records attributed to F Schneider.

At least 343 records · Page 19Linked to original sources
PubMed1976

Chemical investigations on pig kidney aminoacylase.

1. Preparations of purified pig kidney aminoacylase (N-Acylamino-acid amidohydrolase, EC 3.5.1.14) were obtained by Sephadex and DEAE-cellulose chromatography in homogeneous form as judged by polyacrylamide gel electrophoresis and immunoelectrophoresis. 2. The apparent molecular weight of the enzyme, determined by gel filtration, was about 86 000. After treatment with mercaptoethanol, performic acid or sodium dodecyl sulphate a band with an apparent molecular weight of approximately 43 000 was observed in polyacrylamide gels containing sodium dodecyl sulphate. Thus pig kidney aminoacylase seems to be composed of two subunits. 3. The amino acid composition of the enzyme was determined. Aminoacylase contains 772 amino acids, which corresponds to a molecular weight of 85 500. 12 tryptophan and 12 half-cystine residues were found. 4. Each subunit of the enzyme contains two -SH groups of different reactivity and two disulfide bonds one of which is easily cleaved by -SH compounds, the second only by performic acid oxidation. 5. Chemical modification of two -SH groups abolishes the catalytic activity of aminoacylase. Cleavage of two disulfide bonds also inactivates the enzyme. It is suggested that the enzyme has two active sites each containing an essential -SH group and disulfide bond. One active site is assumed to be part of each subunit.

Amidohydrolases↗
PubMed1976

[Double pylorus (author's transl)].

Two cases of double pylorus are reported which had been diagnosed gastroscopically. In 1 case, the ulcerative origin could be demonstrated by autopsy and histological examination.

Congenital Abnormalities↗
PubMed1976

Chemical modification of two tryptophan residues abolishes the catalytic activity of aminoacylase.

1) The reaction of 1 H-diazotetrazole and N-bromosuccinimide with aminoacylase was studied under different conditions. A tenfold molar excess of 1 H-diazotetrazole (2 X 10(-4) M) at pH 5.5 abolishes the catalytic activity of the enzyme while modifying only two tryptophan residues. No other amino acid reacted under these conditions as tested by amino acid analysis. 2) With a 40-fold molar excess of N-bromosuccinimide (8 X 10(-4)M) at pH 5.0, two tryptophan residues of the enzyme were oxidized with complete loss of activity. Under these conditions no significant cleavage of the polypeptide chain was observed. Neither tyrosine nor histidine was modified by this reagent, up to a 100-fold molar excess. 3) Substrates and reversible (N-tosylalanine) and irreversible (TosPheCH2Cl) inhibitors of the enzyme do not protect the two reactive tryptophans against the modification reagents. Under more drastic conditions, lysine, tyrosine and histidine residues are also modified by the reagents.

Alanine↗
PubMed1975

The pH-dependence of the peptidase activity of aminoacylase.

Aminoacylase is a potent peptidase around pH 8.5. The pH dependence of the Km values reveals that only dipeptides with uncharged N-terminal amino acids are substrates of the enzyme. The Km values reflect the hydrophobicity of the N-terminal amino acids. Calculated on the basis of unprotonated peptides they are pH independent. Hydrophobic, deprotonated amino acids are competitive inhibitors of the enzyme, tryptophan and norleucine being the strongest inhibitors. Inhibitor constants with glycylalanine as substrate have been determined for several amino acids. From the present results it may be deduced that the N-terminal amino acids of dipeptides are bound at a strongly hydrophobic site.

Amidohydrolases↗