Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: KEGG:D02011 (FAD)
 5,530 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitric oxide (NO) synthases (NOS) are thiolate-ligated heme-, tetrahydrobiopterin (BH(4))-, and flavin-containing monooxygenases which catalyze the NADPH-dependent conversion of L-arginine (L-Arg) to NO AND citrulline. NOS consists of two domains: an N-terminal oxygenase (heme- and BH(4)-bound) domain and a C-terminal reductase (FMN- and FAD-bound) domain. In this study, we have spectroscopically examined the binding of L-Agr and BH(4) to the dimeric, BH(4)-free ferric neuronal NOS (NNOS) oxygenase domain expressed in Escherichia coli separately from the reductase domain. Addition of L-Arg or its analogue inhibitors (N(G)()-methyl-L-Arg, N(G)()-nitro-L-Arg) and BH(4), together with dithiothreitol (DTT), to the pterin-free ferric low-spin oxygenase domain (gamma(MAX): 419, 538, 568 NM) and incubation for 2-3 days at 4 degrees C converted the domain to a native enzyme-type, predominantly high-spin state (gamma(MAX): approximately 395, approximately 512, approximately 650 NM). 7,8-Dihydrobiopterin and other thiols (E.G., beta-mercaptoethanol, cysteine, and glutathione, with less effectiveness) can replace BH(4) and DTT, respectively. the UV-visible absorption spectrum of L-Arg-bound ferric full length NNOS, which exhibits a relatively intense band at approximately 650 NM (epsilon equals 7.5-8 MM(-)(1) CM(-)(1)) due to the presence of a neutral flavin semiquinone, can then be quantitatively reconstructed by combining the spectra of equimolar amounts of the oxygenase and reductase domains. Of particular note, the heme spin-state conversion does not occur in the absence of a thiol even after prolonged (35-48 H) incubation of the oxygenase domain with BH(4) and/or L-Arg under anaerobic conditions. Thus, DTT (or other thiols) plays a significant role(s) beyond keeping BH(4) in its reduced form, In restoring the pterin- and/or substrate-binding capability of the E. coli-expressed, BH(4) free, dimeric NNOS oxygenase domain. Our results in combination with recently available X-ray crystallography and site-directed mutagenesis data suggest that the observed DTT effects arise from the involvement of an intersubunit disulfide bond or its rearrangement in the NOS dimer.
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PMID:Essential thiol requirement to restore pterin- or substrate-binding capability and to regenerate native enzyme-type high-spin heme spectra in the Escherichia coli-expressed tetrahydrobiopterin-free oxygenase domain of neuronal nitric oxide synthase. 1062 50

Although Rhodococcus spp. strains are able to degrade methoxyphenols by enzymatic means, the contact with veratric acid (3, 4-dimethoxybenzoic acid, hereafter called veratrate) is very stressful for the cells of Rhodococcus erythropolis DSM 1069 (Rh). Within 5 min of contact veratrate in phosphate buffer, the emergence of many vacuoles was observed in the cell body and respiratory bursts, with violent endogenous oxygen uptake, took place several times during the 24 h incubation. During these peaks (where the cells were in their MAX states), increased activity of NADH oxidase was noted, accompanied by maximal accumulation of vanillic and isovanillic acids (3-methoxy-4-hydroxybenzoic acid and 4-hydroxy-3-methoxybenzoic acid respectively, hereafter called vanillates) in the incubation medium, which appeared to be products of veratrate demethylation. At the troughs (cell in their MIN state), the vacuoles disappeared from the cell body, oxygen uptake was normal, and the pool of vanillates decreased while the veratrate level in the medium increased. The cells from MAX and MIN states reacted in opposite ways in the presence of either formaldehyde and GSH, or paraquate and cAMP. The NADH oxidase activity, measured as oxygen uptake against NADH in the membrane pellets of MAX and MIN stage cells, differed in their response to the exogenous presence of FAD, ATP, cAMP, catalase, GSH, H(2)O(2)and methoxyphenolic substrates. The periodic character of these events is described here. Co-operation between two multiprotein membrane complexes (NAD(P)H oxidase and 3-O/4-O-demethylases) in Rhodococcus erythropolis cells and their competition for two common substrates-NAD(P)H and O(2)-is proposed as an explanation for rhythmical nature of these reactions.
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PMID:Multiple respiratory bursts as a response to veratrate stress in Rhodococcus erythropolis cells. 1092 25