Sulphite oxidase

Sulphite Oxidase.— The molybdenum site of sulphite oxidase has been investigated by EXAFS in its iv, v, and vi oxidation states. The highest oxidation level has two cw-M=0 bonds with strong cis-S donors which are trans to each other. Two further S donors are also proposed at longer distances (4), Similar co-ordination has been achieved in a model complex with a quadridentate ligand and shows similar EXAFS behaviour. 

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Deficiency of molybdenum cofactor can lead to sulphite oxidase deficiency (Anke and Glei 1994). 

Of the mammalian enzymes, the sulphite oxidase of bovine liver has only recently been discovered to contain molybdenum (15). The better known molybdenum enzymes, xanthine oxidase from cows milk (31) and aldehyde oxidase from rabbit liver (16) are closely related to one another as they are to the xanthine dehydrogenases from chicken liver (17) and from bacteria (18). 

Fig. 7. Effect of pH on the EPR spectrum recorded at —100° of sulphite oxidase reduced by sulphite. The species present at low pH values, which shows proton splitting, is replaced by another species at high pH. The pH. for the transformation is about 8.2, In (A), maxima and minima in the derivative spectra are denoted by the numbers 1—7. In (B) changes in the spectra are plotted as a function of pH. with values at pH 7.2 taken as 100% and those at pH 9.2 taken as 0%, or vice versa. The features in the spectra measured were height of the 1 and 2 doublet (open circles) height of the peak at 3 (squares) distance between 4 and 5 (triangles) and height of 7 (diagonal crosses). (Reproduced from ref. 15, with the permission of Dr. K. V. Rajagopalan.)...

Jolivet P, Bergeron E, Meunier J-C. Evidence for sulphite oxidase activity in spinach leaves. Phytochemistry 1995 40 667-672. 

A large elevation of Hey in body fluids and tissues is found in several genetic enzyme deficiencies, the homocystinurias. These include cystathionine /3-synlhase deficiency [9], the remethylation defects due to deficiency of MTHF reductase [10], methionine synthase and methionine synthase reductase deficiencies, as well as defects of intracellular cobalamin metabolism [11], namely the cblF, cblC and cblD defects. It is noteworthy that low levels of total Hey (tHcy) have been described in sulphite oxidase deficiency [12]. 

Sass JO, Nakanishi T, SatoT, ShimizuA (2004) New approaches towards laboratory diagnosis of isolated sulphite oxidase deficiency. Ann Clin Biochem 41 157-159... 

A.K. Abass, J.P. Hart and D. Cowell, Development of an amperometric sulphite biosensor based on sulphite oxidase with cytochrome c, as electron acceptor, and a screen-printed transducer, Sens. Actuators B Chem., 62 (2000) 148-153. 

Fig. 3.1. A, The respiratory chain. Q and c stand for ubiquinone and cytochrome c, respectively. Auxiliary enzymes that reduce ubiquinone include succinate dehydrogenase (Complex II), a-glycerophosphate dehydrogenase and the electron-transferring flavoprotein (ETF) of fatty acid oxidation. Auxiliary enzymes that reduce cytochrome c include sulphite oxidase. B, Thermodynamic view of the respiratory chain in the resting state (State 4). Approximate values are calculated according to the Nernst equation using oxidoreduction states from work by Muraoka and Slater, (NAD, Q, cytochromes c c, and a oxidation of succinate [6]), and Wilson and Erecinska (b-562 and b-566 [7]). The NAD, Q, cytochrome b-562 and oxygen/water couples are assumed to equilibrate protonically with the M phase at pH 8 [7,8]. E j (A ,/ApH) for NAD, Q, 6-562, and oxygen/water are taken as —320 mV ( — 30 mV/pH), 66 mV (- 60 mV/pH), 40 mV (- 60 mV/pH), and 800 mV (- 60 mV/pH) [7-10]. FMN and the FeS centres of Complex I (except N-2) are assumed to be in redox equilibrium with the NAD/NADH couple, FeS(N-2) with ubiquinone [11], and cytochrome c, and the Rieske FeS centre with cytochrome c [10]. The position of cytochrome a in the figure stems from its redox state [6] and its apparent effective E -, 285 mV in...

Five proteins containing molybdenum are known nitrate reductase, nit-rogenase, xanthine oxidase, aldehyde oxidase and sulphite oxidase. They also contain iron, and the first four are best classified as multi-enzyme systems. Early studies on xanthine oxidase used a number of important ESR techniques, particularly rapid freeze kinetic methods and isotopic substitution in metalloproteins. This work has been reviewed [38, 39], Nitrogenase is the subject of considerable recent interest since it contains detectable iron-sulphur centres but as there is some disagreement at present concerning the interpretations of the results readers are referred to the original literature [40-42]. 

Figure 4.6. Sulphite oxidase [43]. (A) Showing proton splitting and effect of D2O. (B) At pH 9.2, 9.6. (C) Showing molybdenum nuclear hyperfine lines (6)...

The problems of identification are not nearly so acute when dealing with metalloproteins as they have a wide range of g values, and a number of these have been observed in whole tissue. Thus, the low spin ferric form of cytochrome P-450 has been observed in liver and its concentration found to be reduced in Morris hepatomas [82]. Adrenal ferredoxin in adrenal glands [83], sulphite oxidase in liver [84], iron-sulphur proteins in pigeon heart [85], methaemoglobin and erythrocyte catalase in whole blood are further examples in mammals. 

Heme Cytochrome c Cytochrome c oxidase, cytochrome c peroxidase, cellobiose dehydrogenase, nitrate reductase, sulphite oxidase, theophylline oxidase, cytochrome 62... 

A. Mulchandani, et. al, Determination of sulphite in food products by an enzyme electrode, J. Biotechnol. 18 (1-2), 93-102 (1991). (sulphite oxidase enzyme). 

Yamanaka T, Yoshioka T, Kimura K (1981b) Purification of sulphite-cytochrome c reductase of Thiobacillus novellus and reconstitution of its sulphite oxidase system with the purified constituents. Plant Cell Physiol 22 613-622... 

Molybdenum cofactor deficiency (MoCoD) is an autosomal recessive, fatal neurological disorder, characterized by the combined deficiency of sulphite oxidase, xanthine dehydrogenase, and aldehyde oxidase. No therapy is known for this rare disease, which results in neonatal seizures and other neurological symptoms identical to sulfite oxidase deficiency. Heterozygous carriers of a MoCo deficiency allele do not display any symptoms (Reiss et al. 1999). 

The sulphite oxidase family Fig. 18.2 The major families of mononuclear molybdenum enzymes (Hille 1996). 

Johnson JL, Rajagopaian KV, Lanman JT et al. (1991) Prenatal diagnosis of molybdenum cofactor deficiency by assay of sulphite oxidase activity in chorionic villus samples. J Inher Metab Dis 14 932-937. 

Roesel RA, Bowyee E, Blankenship PR and Hommes EA (1986) Combined xanthine and sulphite oxidase defect due to a deficiency of molybdenum cofactor. J Inher Metab Dis 9 343-347. 

Roth A, Nogues C, Monnet JP, Ogier H and Saudubray JM (1985) Anatomo-pathological findings in a case of combined deficiency of sulphite oxidase and xanthine oxidase with a defect of molybdenum cofactor. Virchows Archiv (Pathol Anat) 405 379-386. 

Sulphite oxidase Sulphonyl haloamines (aromat.) Sulphur dioxide Surfactants... 

M. Masoom and A. Townshend, Flow-Injection Determination of Sulphite and Assay of Sulphite Oxidase. Anal. Chim. Acta, 179 (1986) 399. 

RC Bray, MT Lamy, S Gutteridge, T Wilkinson. Evidence from electron-paramagnetic-resonance spectroscopy for a complex of sulphite ions with the molybdenum center of sulphite oxidase. Biochem J 201 241, 1982. 

NAKAMURA, T., MEYER, C., SANO, H., Molecular cloning and characterization of plant genes encoding novel peroxisomal molybdoenzymes of the sulphite oxidase family, 7. Exp. Bot., 2002, S3, 1833-1836. 

Another important naturally occurring pteridine is molybdopterin, apparently (9.28), which is the coenzyme of xanthine dehydrogenase, aldehyde oxidase, nitrate reductase, sulphite oxidase and presumably other enzymes that need both molybdenum and iron to function (Johnson and Rajagopolan, 1982). Xanthopterin, a co-lymphokine (p. 182), inhibits proliferation of lymphocytes (Ziegler 1983). 

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