The acid-base chemistry that drives catalysis in pyridoxal-5'-phosphate (PLP)-dependent enzymes has been the subject of intense interest and investigation since the initial identification of PLP's role as a coenzyme in this extensive class of enzymes. It was first proposed over 50 years ago that the initial step in the catalytic cycle is facilitated by a protonated Schiff base form of the holoe...

The thionicotinamide analogues of NAD+ and NADP+ were shown to be good alternative coenzymes for bovine glutamate dehydrogenase, with similar affinity and approx. 40% of the maximum velocity obtained with the natural coenzymes. Both thionicotinamide analogues show non-linear Lineweaver-Burk plots, which with the natural coenzymes have been attributed to negative co-operativity. Since the reduce...

that the molecular structure of an auxin may control its activity in growth by influencing the reaction reported here. On the basis of these experiments it is proposed that auxin may act in plant growth and metabolism at least in part by reacting with coenzyme A. It may be assumed that the reaction product is a high-energy ester like the thiol-esters of other acids with coenzyme A. From its pos...

Lead is a persistent and common environmental contaminant, which chiefly plays a significant role in modern industry. Coenzyme Q acts as electron and proton carrier in mitochondria and functions as an antioxidant in its reduced form (ubiquinol). To investigate the hazardous effects of lead on the coenzyme Q level, rats were injected i.p. with lead acetate (5 mg/kg b.wt. daily for 6 weeks). Our ...

The terminal enzyme of the NADH-dependent stearyl coenzyme A desaturase system has been isolated from rat liver microsomes. This desaturase is a single polypeptide of 53,000 daltons containing 62% nonpolar amino-acid residues and one atom of non-heme iron. The purified protein forms high molecular weight aggregates that can be dispersed by detergent procedures. Desaturase activity requires NADH...

Megraw, Robert E. (Albert Einstein Medical Center, Philadelphia, Pa.), Henry C. Reeves, and Samuel J. Ajl. Formation of lactyl-coenzyme A and pyruvyl-coenzyme A from lactic acid by Escherichia coli. J. Bacteriol. 90:984-988. 1965.-Cell extracts of propionate-adapted Escherichia coli were found to contain a lactyl-coenzyme A (CoA) synthetase which catalyzes the formation of the CoA thiolester fr...

Nicotinamide-(S-methylmercury-thioinosine) dinucleotide was formed by reaction of nicotinamide-(6-thiopurine) dinucleotide with methylmercury chloride. The compound exhibits coenzyme properties in the test with LDH (Km=1.5 X 10(-4) M, Vmax=12500) and LADH (Km=1.7 X 10(-4) M, Vmax=27) and inactivates YADH and GAPDH. From incubations with LDH and LADH the mercury containing coenzyme could be reg...

All-trans-retinoic acid is metabolized to a less polar metabolite in rat liver microsomes. This metabolite was proven to be ethyl retinoate by cochromatography on high-performance liquid chromatography, base hydrolysis to all-trans-retinoic acid, and gas chromatography/mass spectral analysis. The formation of ethyl retinoate is a specific enzymatic process; the apparent Km for all-trans-retinoi...

Although several values for tissue phosphoglucomutase activites are recorded in the literature, such determinations have been performed without the addition of the coenzyme, a-glucose 1,6-diphosphate (l-3), and occasionally without explicit designation of the optimal concentrations of either or both of the known activators, Mg++ and amino acid (2, 3). Although some of these latter factors have ...

Acetyl coenzyme A synthetase, which catalyzes the biosynthesis of acetyl coenzyme A from acetat,e, adenosine triphosphate, and coenzyme A, has previously been obtained in highly purified form from bovine heart mitochondria (1). The enzyme appeared to be fairly homogeneous because only a single protein peak was detected in two chromatographic systems and the pattern observed in the analytical ul...