Stoicheiometric amounts of [14C]disulfiram react rapidly with sheep liver cytoplasmic aldehyde dehydrogenase to give loss of catalytic activity and incorporation of the expected amount of radioactivity. In a subsequent slower reaction the label is lost from the enzyme without re-emergence of enzymic activity. The results imply that in vivo disulfiram may act as an oxidation-reduction catalyst f...

We describe a procedure for assay of diaphorase activity in commercial purified preparations and in clinical chemical reagents by use of iodonitrotetrazolium chloride or other tetrazolium salts. The method is based on measurement of the formazan produced by enzymic reduction of tetrazolium salts in the presence of NADH. The assay procedure has been optimized for linear kinetics, simplicity of o...

The conversion of phytoene into beta-carotene was demonstrated previously in chromoplast membranes prepared from Capsicum fruits (B. Camara et al. 1982 Eur J Biochem 127: 255-258). The direct cyclization of lycopene into beta-carotene and the successful solubilization of the enzymic activity involved in this reaction is reported.

Orthovanadate was shown to be a potent competitive inhibitor (Ki less than 1 microM) of purified alkaline phosphatase from human liver, intestine of kidney. Inhibition was reversed and full enzymic activity restored in the presence of 1mM-adrenaline. Phosphate and vanadate competed for the same binding site on the enzyme.

A spectrophotometric method using umbelliferone derivatives has been developed for the study of enzymic activites of mycobacteria. Arylsulphatase activity can be estimated in six hours rather than in 10 days as in the conventional method. The technique may be applied to a study of whole cells or to cell-free extracts.

The Growth of Coxiella burnetii in Embryonated Eggs. RICHARD A. ORMSBEE........................................................... 73 Growth and Hydrogenase Activity of a New Bacterium, Hydrogenomonas facilis. ALBERT SCHATZ AND CARLTON BOVELL, JR................... 87 Separation of Encephalomyocarditis Virus from Tissue Components by Means of Protamine Precipitation and Enzymic Digestion. MARVI...

Diffusional effects on two-substrate enzymic reactions mainly depend on the relative affinities of the enzyme for its two substrates. With two substrates of widely different affinities, diffusional limitations increase and decrease the half-maximal-activity concentration of the high-and low-affinity substrate respectively.

Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase, the system responsible for the formation of the chlorophyll isocyclic ring in developing cucumber (Cucumis sativus L. cv Beit Alpha) chloroplasts, was resolved into two enzymic components: a high-speed supernatant and a membrane pellet. This reconstituted enzyme system required reduced pyridine nucleotide for activity.

Beef heart aconitase has been studied by low temperature magnetic circular dichroism (MCD) spectroscopy in the wavelength region 300 to 1900 nm. Together with parallel electron paramagnetic resonance and activity measurements, these data enable correlations between Fe-S cluster-type and enzymic activity in aconitase. In samples not exposed to extraneous Fe, the Fe-S cluster in aconitase exhibit...

Prostaglandin endoperoxide synthase (PES, EC 1.14.99.1) catalyse the conversion of arachidonic acid into prostaglandin H2. The enzyme is a 140 kDa homodimer which contains both a cyclo-oxygenase activity (converting arachidonate into prostaglandin G2) and peroxidase activity (reducing prostaglandin G2 to H2). PES undergoes rapid self-inactivation during oxygenation of arachidonate to prostaglan...