Assay of human serum and liver guanase activity with 8-aza-guanine as substrate

Ellis, Graham; Goldberg, David M.

doi:10.1016/0009-8981(72)90414-7

Cited by 12 publications

(2 citation statements)

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“…The other product of the guanase reaction, the ammonia, can be used for determination of the enzyme activity as well. After incubation of sera, and tissue samples with guanine or azaguanine, ammonia is measured colorimetrically (4,12,27,39). Coupling the liberation of am monia during guanase reaction with the gluta mate dehydrogenase system results in a con tinuous method in which the decrease of the NADH concentration is recorded at 340, 334 or 366 nm (11,13,44).…”

Section: Introductionmentioning

confidence: 99%

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A New Spectrophotometric Assay for Enzymes of Purine Metabolism

Heinz¹,

Reckel²,

Kalden³

1979

Enzyme

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A new method for the determination of guanase is described. Xanthine, the product of the guanase reaction, is oxidized by xanthine oxidase, forming uric acid and hydrogen peroxide. Hydrogen peroxide is further reduced to water by catalase in the presence of ethanol. The acetaldehyde formed in this reaction step is dehydrogenated NAD or NADP dependent by aldehyde dehydrogenase. The NADH or NADPH production is measured and utilized for the calculation of the guanase activity. The sensitivity of the method can be doubled by the addition of uricase, which oxidizes uric acid to permit the formation of another mole of hydrogen peroxide.

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Section: Introductionmentioning

confidence: 99%

“…trum in the range of 254-240 nm, which fol lows the deamination of guanine to xanthine (20,21,23) or 8-azaguanine to 8-azaxanthine respectively (12,40). In another UV method, xanthine, one prod uct of the guanase reaction, is oxidized to uric acid by xanthine oxidase.…”

Section: Introductionmentioning

confidence: 99%