1. The inhibition of pepsin-catalysed hydrolysis of N-acetyl-l-phenylalanyl-l-phenylalanylglycine by products and product analogues was studied. 2. The non-competitive nature of the inhibition by the product N-acetyl-l-phenylalanine confirms an ordered release of products, and points to a common mechanism (involving an amino-enzyme) for pepsin-catalysed transpeptidation and hydrolysis reactions...

The enzymic 5'-deiodination of 3',5'-di-iodothyronine and 5-deiodination of 3,3',5-tri-iodothyronine by rat liver microsomal fractions were found to be characterized by apparent Km values of 0.77 and 17.4 microM respectively, 3',5'-Di-iodothyronine was a competitive inhibitor of 3,3',5-tri-iodothyronine 5-deiodination (Ki 0.65 microM) and 3,3',5-tri-iodothyronine was a competitive inhibitor of ...

Four new compounds have been synthesized as potential inhibitors of dihydroorotase from Escherichia coli. NMR spectroscopy was used to show that 4,6-dioxo-piperidine-2(S)-carboxylic acid (3), exists in solution as a mixture of the hydrate (7), enol (8), and enolate (9) tautomeric forms. This compound was found to be a competitive inhibitor versus dihydroorotate and thio-dihydroorotate at pH val...

Phenazine methosulfate was shown to be a competitive inhibitor of H+ in light-induced H+ transport as well as a competitive inhibitor of orthophosphate in photophosphorylation. Similarly, H+, NH4+, and Pi in the presence of adenosine diphosphate were shown to inhibit competitively light-induced binding of phenazine methosulfate to chloroplasts. Pi, in the absence of ADP or other anions such as ...

During a study of the reduction of cytochrome c by milk xanthine oxidase, it was observed that relatively impure preparations of cytochrome c were reduced more slowly than highly purified preparations. This difference was found to relate to the presence, in impure preparations, of a potent inhibitor of the reduction of cytochrome c by xanthine oxidase. This inhibitor was of interest because its...

During a study of the reduction of cytochrome c by milk xanthine oxidase, it was observed that relatively impure preparations of cytochrome c were reduced more slowly than highly purified preparations. This difference was found to relate to the presence, in impure preparations, of a potent inhibitor of the reduction of cytochrome c by xanthine oxidase. This inhibitor was of interest because its...

A diversified library of peptide anilides was prepared, and their inhibition activities against the SARS-CoV 3CL protease were examined by a fluorogenic tetradecapeptide substrate. The most potent inhibitor is an anilide derived from 2-chloro-4-nitroaniline, l-phenylalanine and 4-(dimethylamino)benzoic acid. This anilide is a competitive inhibitor of the SARS-CoV 3CL protease with K(i) = 0.03 m...

Studies were carried out to natural papain inhibitor from papaya latex. Fresh latex from green fruits of Carica papaya was collected and immediately transported in ice bath to the lab, from which three fractions with inhibitor effect of esterase papain activity were isolated by latex dialysis, Sephadex G-25 gel filtration and ionic exchange chromatography in SP-Sephadex C-25. The isolated fract...

BACKGROUND Investigations into the regulation and functional roles of kinases such as cAMP-dependent protein kinase (PKA) increasingly rely on cellular assays. Currently, there are a number of bioluminescence-based assays, for example reporter gene assays, that allow the study of the regulation, activity, and functional effects of PKA in the cellular context. Additionally there are continuing e...

p300/CBP-associated factor (PCAF) is a histone acetyltransferase that plays an important role in the remodeling of chromatin and the regulation of gene expression. It has been shown to catalyze preferentially acetylation of the epsilon-amino group of lysine 14 in histone H3. In this study, the kinetic mechanism of PCAF was evaluated with a 20-amino acid peptide substrate derived from the amino ...