The specificity of sulfonium stereoisomers in some enzyme systems

Zappia, Vincenzo; Zydek-Cwick, Cynthia R.; Schlenk, F.

doi:10.1016/0005-2744(69)90147-8

Cited by 38 publications

(34 citation statements)

References 9 publications

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“…This interpretation does not take into account possible conformational changes of the thioether caused by the chemical modifications. A similar binding has been proposed for S-adenosylmethionine and S-adenosylhomocysteine to methyl-transfer enzymes (Zappia et al, 1969;Borchardt, 1977).…”

Section: Discussionsupporting

confidence: 65%

“…The inhibitory effect exerted by 5'-methylthioadenosine on some methyltransferases (Zappia et al, 1969) suggests that the enzymic cleavage(s) of the thioether can also regulate this class of reactions.…”

mentioning

confidence: 99%

“…The chemical and radiochemical purity of 5'-methylthioadenosine and S-adenosylmethionine was checked by t.l.c. and high-voltage electrophoresis (Zappia et al, 1969(Zappia et al, , 1977b. The u.v.…”

mentioning

confidence: 99%

“…5'-Methylselenoadenosine was prepared by acid hydrolysis of S-adenosyl-L-selenomethionine . The selenonium compound has been enzymically synthesized from L-selenomethionine and ATP (Stekol, 1965); the thioether has been isolated from its precursor by ion-exchange chromatography (Zappia et al, 1969 (Parks, 1958). Labelled 5'-ethylthioadenosine was then converted into the inosine analogue as previously described, the kinetics of deamination being similar to that of 5'-methylthioadenosine.…”

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confidence: 99%

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Substrate specificity of 5′-methylthioadenosine phosphorylase from human prostate

Zappia¹,

Oliva²,

Cacciapuoti³

et al. 1978

Biochemical Journal

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5'-Methylthioadenosine phosphorylase was purified approx. 340-fold from human prostate by using affinity chromatography by Hg-coupled Sepharose. The enzyme, responsible for the breakdown of 5'-methylthioadenosine into adenine and methylthioribose 1-phosphate, was partially characterized. The apparent Km for 5'-methylthioadenosine is 25,uM. It is activated by thiols and shows an absolute requirement for phosphate ions. New analogues of 5'-methylthioadenosine were prepared and their activity as substrates or inhibitors of the reaction was investigated. The replacement of the 6-amino group of the adenine moiety by a hydroxy group, as well as the replacement of N-7 by a methinic radical, resulted in an almost complete loss ofactivity. Otherwise the replacement of sulphur by selenium, as well as that of the methyl group by an ethyl one, is compatible with the activity as substrate. The positively charged sulphonium group also prevents catalytic interaction with the enzyme. The inhibitory effect of 5'-methylthiotubercidin (competitive) and 5'-dimethylthioadenosine sulphonium salt (non-competitive) was also demonstrated. The reported results suggest three binding sites between the substrate and the enzyme.

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Section: Discussionsupporting

confidence: 65%

mentioning

confidence: 99%

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confidence: 99%

mentioning

confidence: 99%

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Substrate specificity of 5′-methylthioadenosine phosphorylase from human prostate

Zappia¹,

Oliva²,

Cacciapuoti³

et al. 1978

Biochemical Journal

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“…It is well known that AdoMet-dependent methyltransfer reactions are involved in a wide variety of important biological processes in bothprokrayoQtes and eukaryotes (Cantoni & Chiang, 1980) and that AdoHcyw is a 'general' inhibitor of this class of reactions (Zappia et al, 1969;Cox et al, 1977;Ueland, 1982). Thus a regulatory role of the AdoHcy cellular concentration (or AdoHcy/AdoMet ratio) on the methylation-dependent processes has been proposed (Cantoni & Chiang, 1980).…”

Section: Introductionmentioning

confidence: 99%

Escherichia coli S-adenosylhomocysteine/5′-methylthioadenosine nucleosidase. Purification, substrate specificity and mechanism of action

Ragione

Porcelli

Cartenı́-Farina

et al. 1985

Biochemical Journal

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S-Adenosylhomocysteine/5'-methylthioadenosine nucleosidase (EC 3.2.2.9) was purified to homogeneity from Escherichia coli to a final specific activity of 373 ,umol of 5'-methylthioadenosine cleaved/min per mg of protein. Affinity chromatography on S-formycinylhomocysteine-Sepharose is the key step of the purification procedure. The enzyme, responsible for the cleavage of the glycosidic bond of both Sadenosylhomocysteine and 5'-methylthioadenosine, was partially characterized. The apparent Km for 5'-methylthioadenosine is 0.4 /LM, and that for S-adenosylhomocysteine is 4.3 /tM. The maximal rate of cleavage of S-adenosylhomocysteine is approx. 40% of that of 5'-methylthioadenosine. Some 25 analogues of the two naturally occurring thioethers were studied as potential substrates or inhibitors of the enzyme. Except for the analogues modified in the 5'-position of the ribose moiety or the 2-position of the purine ring, none of the compounds tested was effective as a substrate. Moreover, 5'-methylthioformycin, 5'-chloroformycin, S-formycinylhomocysteine, 5'-methylthiotubercidin and S-tubercidinylhomocysteine were powerful inhibitors of the enzyme activity. The results obtained allow the hypothesis of a mechanism of enzymic catalysis requiring as a key step the protonation of N-7 of the purine ring.

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Biosynthesis and Metabolism of 1,4‐diaminobutane, Spermidine, Spermine, and Related Amines

Tabor¹,

Tabor²

1972

Advances in Enzymology - And Related Areas of Molecular Biology

101

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The specificity of sulfonium stereoisomers in some enzyme systems

Cited by 38 publications

References 9 publications

Substrate specificity of 5′-methylthioadenosine phosphorylase from human prostate

Substrate specificity of 5′-methylthioadenosine phosphorylase from human prostate

Escherichia coli S-adenosylhomocysteine/5′-methylthioadenosine nucleosidase. Purification, substrate specificity and mechanism of action

Biosynthesis and Metabolism of 1,4‐diaminobutane, Spermidine, Spermine, and Related Amines

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