Accumulation of xanthine as well as uric acid, was found as a result of hypoxanthine oxidation by xanthine : oxygen oxidoreductase from milk. The ratio xanthineluric acid increases with hypoxanthine concentration, and decreases with the enzyme concentration and the reaction time. The methodical consequences of the xanthine accumulation during hypoxanthine oxidation are discussed. The possibility of regulation of the xanthineluric acid ratio in the cell by changes of enzyme and/or hypoxanthine levels is suggested.Hypoxanthine oxidation (hydroxylation) in living cells is believed to be a two-step reaction :Hypoxanthine --, Xanthine -Uric Acid catalysed by one enzyme, xanthine oxidase.suggested that a pool of xanthine may arise in vivo during hypoxanthine oxidation. Transient accumulation of xanthine by the milk enzyme in vitro was reported by Bergmann and Dikstein [2]. Xanthine is also accumulated by the action of xanthine dehydrogenase from chicken [3] and from snail, Helix pomatiu [4], on hypoxanthine. It seems that this enzyme may play some role in the regulation of the xanthineluric acid ratio in living organisms. The present study was undertaken with the aim of obtaining some information about the pools of these two purines arising in the course of hypoxanthine oxidation.The model enzyme, xanthine : oxygen oxidoreductase from milk, was used for this purpose. I I1 MATERIALS AND METHODS ReagentsXanthine oxidase (milk) preparations were purchased from P-L Biochemicals, Inc. (Milwaukee, Vis., U.S.A.) and Koch-Light Laboratories Ltd (Colnbrook, Bucks, England) ; they were used without further purification. The ratios of absorbance a t 280 and 450 nm for these preparations were found to be 11.6 and 9.0, respectively; the preparations were stored a t 4 "C and were diluted 1 :lo0 with 0.03 M Tris-RC1 buffer pH 8.0, before use. Highly purified milk xanthine oxidase (batch 31 S, A::? = 29, Enzyme. Xanthine oxidase or xanthine : oxygen oxidoreductase (EC 1.2.3.2).act./A,,, = 159) was the kind gift of Dr R.

ABSTRACT

A spectrophotometric method for the determination of three forms of xanthine oxidoreductase, namely dehydrogenase (D), dehydrogenase-oxidase (D/0) and oxidase (0)

IntroductionIn the majority of patients with inflammatory bowel diseases (IBD) mental health problems are demonstrated in the form of excessive anxiety and unstable emotional reactions. Emotional instability affects the wellbeing of these patients, and also their attitude towards the disease and the course of treatment.AimThe objective of the study is to evaluate psychological factors in patients with IBD, and to compare patients with ulcerative colitis (UC) and patients suffering from Crohn's disease (CD) with respect to intensity of these factors.Material and methodsThe study included 108 patients with IBD. NEO-FFI and type-D Scale were used to evaluate personality traits. Anxiety level was measured with STAI. CECS was used to measure the patients’ tendency to suppress negative emotions.ResultsIn the patients with CD 45% of subjects presented type D personality. In the group of patients with UC, type D personality was found in 38%. The higher levels of neuroticism and extraversion were observed in patients with UC, whereas the patients with CD exhibited a higher level of openness to experience and agreeableness. In patients with CD the levels of state anxiety were elevated, whereas in patients with UC higher scores were both for state and trait anxiety.ConclusionsThere were no statistically significant differences in terms of personality factors in a group of patients with CD and UC. It was found that the majority of patients with IBD suffer elevated or high sense of anxiety.

ABTRACT (Int Marit Health 2013; 64, 4: 221-225)

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The effects of 2-iodosobenzoic acid, 4-chloromercuribenzoate, 5,5'-dithiobis-(2-nitrobenzoic acid) and tetraethylthioperoxydicarbonic diamide (disulphiram) on the NAD+-dependent activity of xanthine oxidoreductase from rat liver were investigated. Only disulphiram converted the NAD+-dependent activity into the O2-dependent activity quantitatively, without changing the xanthine hydroxylation rate. The modification process was a first-order reaction with respect to time (min) and disulphiram concentration (microM). The kinetic data showed that modification of single thiol group is sufficient for loss of the enzymic activity towards NAD+ as electron acceptor. The complete protection afforded by NAD+ against the action of disulphiram suggests that the essential thiol group may be involved in binding of NAD+ to the xanthine oxidoreductase molecule.