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Nicotinic acid hydroxylase molybdenum

Stadtman 1971 Kung et al. 1971). Degradation is initiated by hydroxylation of the ring, and the level of nicotinic acid hydroxylase is snbstantially increased by the addition of selenite to the medinm (Imhoff and Andreesen 1979). Nicotinate hydroxylase from Clostridium barkeri contains molybdenum that is coordinated to seleninm, which is essential for hydroxylase activity (Gladyshev et al. 1994). The most remarkable featnre of the pathway is the mechanism whereby 2-methylene-glntarate is converted into methylitaconate by a coenzyme Bi2-mediated reaction (Knng and Stadtman 1971). [Pg.536]

Gladyshev VN, SV Khangulov, TC Stadtman (1994) Nicotinic acid hydroxylase from Clostridium barkeri electron paramagnetic resonance studies show that selenium is coordinated with molybdenum in the catalytically active selenium-dependent enzyme. Proc Natl Acad Sci USA 91 232-236. [Pg.548]

Another selenium-containing molybdenum hydroxylase that has been isolated from Clostridium barkeri (identical to Eubacterium barkeri) is nicotinic acid hydroxylase (NAH). Clostridium barkeri was isolated initially as a fermentor of nicotinic acid and thus NAH is a key enzyme in the efficient fermentation of nicotinic acid as a source of carbon and energy. NAH contained selenium when purified from cells labeled with Se-selenite. However, this label was lost during denaturing gel electrophoresis and also on heating of the enzyme (Dilworth 1982). Exhaustive analysis of selenium-labeled alkylation products of NAH under various conditions revealed selenium was bound as a labile cofactor (Dilworth 1982), and not as seleno-cysteine. This report was the first to describe a selenium-dependent enzyme that did not contain selenium in the form of selenocysteine. [Pg.166]

Dilworth GL. 1983. Occurrence of molybdenum in the nicotinic acid hydroxylase from Clostridium barkeri. Arch Biochem Biophys 221 565-9. [Pg.168]

This enzyme, as well as nicotinic acid hydroxylase was recently reported by Andreesan to be a selenoenzyme. The discovery of both these enzymes was based on the clever assumption that selenium might well be a component of multisubunit enzymes containing redox centers such as iron-sulfur, flavin, molybdenum, etc. When Clostridium acidiurici was cultured in media with supplemental selenium, an elevated activity of xanthine dehydrogenase was observed. The clostridial enzyme is comparable to mammalian xanthine oxidases in that it contains flavin adeninedinucleotide (FAD), molybdenum and nonheme iron. This enzyme functions in vivo under anaerobic conditions and appears to catalyze the reduction of uric acid to xanthine. Again it will be interesting to learn the form of selenium in this enzyme. [Pg.15]

Nicotinic acid hydroxylase. Nicotinic acid hydroxylase consists of four dissimilar subunits and occurs in forms with different molecular masses. There are 5-7 Fe, one FAD, and one molybdenum molybdopterin per 160 kDa protein. Unusually, nicotinic acid hydroxylase as isolated from Clostridium barkeri contains Mo(V) rather than Mo(VI). By EPR spectroscopy of the enzyme containing either natural-abundance Se or Se (/ = Gladyshev and co-workers showed that Se is directly coordinated, although in an unidentified form to Mo. Furthermore, a flavin radical and two [2Fe-2S] clusters could be observed with EPR spectroscopy. ... [Pg.249]

In the first family, the metal is coordinated by one molecule of the pterin cofactor, while in the second, it is coordinated to two pterin molecules (both in the guanine dinucleotide form, with the two dinucleotides extending from the active site in opposite directions). Some enzymes also contain FejSj clusters (one or more), which do not seem to be directly linked to the Mo centers. The molybdenum hydroxylases invariably possess redox-active sites in addition to the molybdenum center and are found with two basic types of polypeptide architecture. The enzymes metabolizing quinoline-related compounds, and derivatives of nicotinic acid form a separate groups, in which each of the redox active centers are found in separate subunits. Those enzymes possessing flavin subunits are organized as a2jS2A2, with a pair of 2Fe-2S centers in the (3 subunit, the flavin in the (3 subunit, and the molybdenum in the y subunit. [Pg.167]


See other pages where Nicotinic acid hydroxylase molybdenum is mentioned: [Pg.177]    [Pg.177]    [Pg.140]    [Pg.825]    [Pg.825]    [Pg.700]    [Pg.7204]   
See also in sourсe #XX -- [ Pg.662 ]

See also in sourсe #XX -- [ Pg.662 ]

See also in sourсe #XX -- [ Pg.6 , Pg.662 ]




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