Modification of a single carboxylate side chain in pepsin by 1,2-epoxy-3Qnitrophenoxy)propane abolished enzymic activity. The degree of inactivation was related to incorporation of the modifier in a 1: 1 molar ratio. The essential residue was an aspartic acid which is contained in the amino acid sequence Ile-Val-Asp-Thr-Gly-Ser-Ser-Asn. The pH rate profile of enzymic inactivation suggested the ...

DNase I from rabbit urine was purified approx. 3600-fold to apparent homogeneity with a 41% yield by affinity chromatography utilizing DNA-cellulose; the purity of the final preparation was assessed by SDS/PAGE, lack of contamination by other nucleases and production of a monospecific antibody against the enzyme. Although the proteochemical and enzymological properties of the purified enzyme re...

We show here that mouse prion protein (PrP(C)) either as recombinant protein or immunoprecipitated from brain tissue has superoxide dismutase (SOD) activity. SOD activity was also associated with recombinant chicken PrP(C) confirming the evolutionary conserved phenotype suggested by sequence similarity. Acquisition of copper by PrP(C) during protein folding endowed SOD activity on the protein b...

Tyrosinase activity was demonstrated in the sera from melanoma-bearing mice. One, two, and three weeks following tumor transplantation, 12, 80, and 90% of the respective sera from these mice showed positive results. No sera from normal mice had tyrosinase activity. There was a correlation between tumor size and tyrosinase activity, the coefficient of correlation being 0.71. The activity in the ...

A method which uses cyanogen bromide for the quantitative conversion of 4-thiouridine to uridine has been developed. The general nature and the specificity of this reaction has been studied with thiouridine residues present in a hexanucleotide isolated from enzymic digests of Escherichia coli tyrosine transfer ribonucleic acid (tRNA), and also with those present in intact E. coli tyrosine and f...

1. The effects of castration and testosterone treatment on enzymic activities involved in folate coenzyme metabolism in the liver and in accessory sex organs of male adult rats were studied. 2. In the liver of castrated rats the concentration of 10-formyltetrahydrofolate (10-HCO-H(4)folate) synthetase and tetrahydrofolate (H(4)folate) dehydrogenase were significantly decreased whereas that of 5...

Our previous studies on carbohydrate structures of purified porcine spleen cathepsin B indicated that there are two cathepsin B isozymes, each containing a different carbohydrate (Takahashi, T., Schmidt, P.G., and Tang, J. (1984) J. Biol. Chem. 259, 6059-6062). We have now isolated these two enzymes and carried out a comparative study on their structures and enzymic properties. The major isozym...