End-product inhibition of acid production in Streptococcus mutans R9 was investigated by measuring effects of varying concentrations of H+ and of undissociated lactic or acetic acids on acid production rates in the pH stat. H+ caused purely uncompetitive inhibition (inhibition constant Kiu 0.018 mmol 1(-1). Lactic acid caused mixed inhibition with inhibition constants of Kiu 4.24 mmol 1(-1) and...

A purified, NADH-linked, D( -)-specific lactate dehydrogenase from Bufyribocferium rettgeri was shown to be inhibited by ATP. Several other nucleotides were also capable of inhibiting the reaction catalyzed by this enzyme but, at equivalent concentrations, none was found to be as effective as ATP. The inhibition by ATP appears to be of the partially competitive type with respect to NADH. This s...

The enzyme aldose (aldehyde) reductase was partially purified (142-fold) and characterized from Euonymus japonica leaves. The reductase, a dimer, had an average molecular weight of 67,000 as determined by gel filtration on Sephadex G-100. The enzyme was NADPH specific and reduced a broad range of substrates including aldoses, aliphatic aldehydes, and aromatic aldehydes. Maximum activity was obs...

During the course of our research efforts to understand the kinetics of human aldehyde oxidase as a xenobiotic-clearing enzyme, we investigated the effect of eight different inhibitors on the oxidation of the probe substrate phthalazine. Saturation kinetic parameters for phthalazine oxidation in human liver cytosol were found to be the following: K(m) = 8.0 ± 0.4 μM and V(max) = 4.3 ± 0.1 nmol ...

abstract background and objective: highly active antiretroviral therapy (haart) can effectively prevent the progression of hiv-1 replication and increase life expectancy. there are numerous causes of treatment failure and the leading one is drug resistance. thus, we aimed to determine the hiv rt gene drug resistance mutations in patients treated with antiretroviral medications. material and met...

IMPDH (Inosine 5'-monophosphate dehydrogenase) catalyzes a rate-limiting step in the de novo biosynthesis of guanine nucleotides. IMPDH inhibition in sensitive cell types (e.g., lymphocytes) blocks proliferation (by blocking RNA and DNA synthesis as a result of decreased cellular levels of guanine nucleotides). This makes it an interesting target for cancer and autoimmune disorders. Currently a...

change factors? The characterization of the mutations present in GEA1 alleles resistant to brefeldin A shows that the altered positions are clustered on a region of Brefeldin A is a small hydrophobic compound produced the Sec7 domain overlapping with, or very close to, the by toxic fungi that has dramatic effects on mammalian Arf1-binding site (Peyroche et al., 1999). Therefore, the cells. With...

Dehydroepiandrosterone (DHEA) and certain structural analogues block the differentiation of 3T3-L1 mouse embryo fibroblasts to adipocytes. These steroids also are potent uncompetitive inhibitors of mammalian glucose-6-phosphate dehydrogenases (G6PDs). We provide direct evidence that treatment of the 3T3-L1 cells with DHEA and its analogues results in intracellular inhibition of G6PD, which is a...

Inhibition of vascular smooth muscle sodium-potassium-activated adenosine triphosphatase (Na-K-ATPase) has been postulated as a central mechanism in enhancing vascular contractility. In the present study, kinetics of inhibition of Na-K-ATPase by lead, ouabain, and natriuretic hormone (NH) was studied in a purified hog cerebral cortex enzyme preparation. Determination of I50 values for lead, oua...

In recent years, clinical symptoms resulting from West Nile virus (WNV) infection have worsened in severity, with an increased frequency in neuroinvasive diseases among the elderly. As there are presently no successful therapies against WNV for use in humans, continual efforts to develop new chemotherapeutics against this virus are highly desired. The viral NS2B-NS3 protease is a promising targ...