14 S W Y : The incorporation of [ C ] N-ethylmaleimide reveals fast and slowreacting sulfhydryl groups in sarcoplasmic reticulum. Two proteins react with the label: a fast-reacting glycoprotein recently isolate$+(Ikemoto, Cucchiaro and Garcia (1976) J. Cell Biol. 10, 290a), and the Ca -ATPase. Labeling sarcoplasmic reticulum with a maleimide spin label gives a similar pattern. The spectra of ma...

Halogenated tyrosine transaminase has been purified 30-fold from a sonic extract of rat kidney mitochondria. Purification involves ammonium sulfate fractionation and chromatography on diethylaminoethyl cellulose and hydroxylapatite. The purified enzyme is highly specific for tyrosine analogues with halogen substituents in positions 3 or 3 and 5, for thyroid hormones, and, to a lesser extent, fo...

A very rapid procedure for the preparation of phosphoglycerate mutase from chicken breast muscle is presented. Commercially available frozen chicken breasts may be used. The enzyme is obtained in high yields, and the specific activity of the crystalline homogenous preparations is equal to that of the crystalline enzymes from yeast and rabbit muscle. The chicken breast enzyme requires 2,3-diphos...

An intracellular glycerol ester hydrolase (lipase) from Propionibacterium shermanii was recovered from cell-free extracts and purified by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography on diethylaminoethylcellulose. Maximum enzyme activity was observed at pH 7.2 and 47 C when an emulsion of tributyrin was used as substrate. The enzyme was stable between pH 5.5 a...

A large number of the antibiotics have demonstrated chemical reactivity toward compounds containing sulfhydryl groups (1, 2). There have also been observed marked differences in reactivity of individual antibiotics toward various types of sulfhydryl-containing compounds. In the present investigation, the effect of structure of thiol compounds on their ability to react with certain antibacterial...

We have compared the effect of the converting enzyme inhibitors, captopril and enalapril, on two models of gastric ulcers, viz; ethanol and oxyphenbutazone-induced lesions in rats. Both captopril and enalapril did not affect ethanol-induced lesions. While captopril significantly protected against oxyphenbutazone-induced lesions, enalapril aggravated the lesions. This difference is probably due ...

The reaction of bromopyruvate with pyruvate kinase was demonstrated both by noting loss of catalytic activity with time and by incorporation of [14C]pyruvate. The first order rate constant for loss of catalytic activity when plotted as a function of bromopyruvate concentration fit a regular hyperbolic saturation function indicative of the formation of a complex with Ki = 15 mM prior to the inac...

Cisplatin was shown to strongly inhibit the decatenation and relaxation activity of isolated human DNA topoisomerase IIalpha. This inhibition was not accompanied by stabilization of a covalent topoisomerase IIalpha-DNA intermediate. Pretreatment of kinetoplast plasmid DNA (kDNA) or pBR322 DNA with submicromolar concentrations of cisplatin quickly rendered these substrates incompetent in the top...

The A(-) type of glucose 6-phosphate dehydrogenase (EC 1.1.1.49) has been isolated from human erythrocytes deficient in this enzyme. The specific activity of the purified protein is similar to that previously reported for the enzyme isolated from normal, nondeficient erythrocytes. During the purification procedure, a portion of the A(-) enzyme converts spontaneously, from the native "fraction I...

Valine dehydrogenase was purified to homogeneity from the crude extracts of Streptomyces aureofaciens. The molecular weight of the native enzyme was 116,000 by equilibrium ultracentrifugation and 118,000 by size exclusion high-performance liquid chromatography. The enzyme was composed of four subunits with molecular weights of 29,000. The isoelectric point was 5.1. The enzyme required NAD+ as a...