The enzymatic reduction of /Shydroxy-P-methylglutaryl coenzyme A to mevalonic acid has been measured in cellfree systems prepared from the livers of rats maintained under various dietary conditions. It has been shown that the reductase reaction is markedly depressed when cholesterol is fed. This diminished activity has been observed in both the microsomes and in the subsequently solubilized pre...

The absorption spectra of the 5,6-dimethylbenaimidazolylcobamide coenzyme (coenzyme Blz) and its benzimidaeolecontaining analogue (benzimidazolylcobamide coenzyme) are different from that of the adenine-containing analogue (adeninylcobamide’ coenzyme (1, 2)). The most conspicuous difference is in the wave length of the absorbancy maximum in the visible region. The spectra of the two benzimidazo...

When highly purified cobamide-dependent ribonucleotide reductase from Lacfobacillus leichmannii is incubated with synthetically prepared 5,6-dimethylbenzimidazolylcobamide 5’-deoxyadenosyl coenzyme containing tritium attached to carbon atom 5’ of the deoxyadenosyl moiety (DBCC-5’-3H), tritium is transferred from DBCC-5’-3H to Hz0 in a reaction requiring substrate, enzyme, and dithiol reductant....

The specific activities of the succinate dehydrogenase-coenzyme Q(10) reductase in gingival tissue from patients with periodontal disease have been compared with the corresponding specific activities of normal human periodontal tissue. The gingival biopsies from patients having diseased periodontal tissue showed a deficiency of coenzyme Q(10), in contrast to those of the normal periodontal tiss...

Coenzyme F430 is a nickel porphinoid found in all methanogenic bacteria. Extended-X-ray-absorption-fine-structure (e.x.a.f.s.) spectra have been recorded above the nickel K-edge of coenzyme F430 and two model compounds, (5,10,15,20-tetramethylporphinato) nickel(II) and (5,10,15,20-tetramethylchlorinato)-nickel(II). The results show that the four nickel-nitrogen distances in F430 are split, with...

Tropoyl coenzyme A has been synthesized in good yields via the corresponding N-hydroxysuccinimide ester. The UV-spectrum of the purified thioester has an absorption maximum at 257 nm; at this wavelength, a molar extinction coefficient of 19.2 x 10(6) [cm2 mol-1] has been determined. Upon alkaline hydrolysis of the thioester bond a difference spectrum with lambda max at 235 nm (delta epsilon 235...

Isoflavones identified as inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase in soybean paste were assayed using the catalytic portion of Syrian hamster HMG-CoA reductase, and the kinetic values were measured using HMG-CoA and NADPH. The inhibition of HMG-CoA reductase by these inhibitors was competitive with HMG-CoA and noncompetitive with NADPH. Ki values for genistein, d...

This study describes the functional identification of a pair of mechanistically diverse enzymes that catalyze the successive dehydration (CurE ECH1) and decarboxylation (CurF ECH2) of (S)-HMG-ACP to generate a 3-methylcrotonyl-ACP intermediate, the presumed precursor of the cyclopropyl ring in curacin A. The reactions catalyzed by ECH1 and ECH2 are found in a broad cross-section of microbial na...