Characterization of xanthine oxidase from Cellulosimicrobium funkei possessing hypoxanthine-metabolizing activity.

AIMS: Purine-degrading enzymes are favourable as medications and diagnostic tools for hyperuricemia. This study aimed to characterize enzymes isolated from micro-organisms, which may be useful for developing a new prophylaxis for hyperuricemia. METHODS AND RESULTS: Cellulosimicrobium funkei A153 was found to be a good catalyst for hypoxanthine degradation and could oxidize hypoxanthine to xanthine and further to uric acid. The enzyme catalysing this oxidation was purified, and its partial amino acid sequences were examined. Based on this information and genome sequencing results, this xanthine dehydrogenase family protein was cloned and expressed in Rhodococcus erythropolis L88. The recombinant enzyme with a His-tag was characterized. The enzyme was a xanthine oxidase as it could utilize molecular oxygen as an electron acceptor. It was stable under 50°C and exhibited maximum activity at pH 7·0. The kcat , Km and kcat /Km values for xanthine were 1·4 s-1 , 0·22 mmol l-1 and 6·4 s-1  mmol-1  l, respectively. CONCLUSIONS: Xanthine oxidase is favourable for hyperuricemia medication because it oxidizes hypoxanthine, an easily adsorbed purine, to xanthine and further to uric acid, which are hardly adsorbed purines. SIGNIFICANCE AND IMPACT OF THE STUDY: The enzyme is useful for decreasing serum uric acid levels via conversion of easily absorbed purines to hardly absorbed purines in the intestine. Enzymes from micro-organisms may be used as a novel prophylaxis for hyperuricemia.

The association of periodontal disease with oral malodour in a Japanese population.

AIM: The purpose of this study was to evaluate the association between oral malodour and periodontal disease, and to determine the effect of periodontal therapy on oral malodour. MATERIALS AND METHODS: Oral malodour parameters, including volatile sulphur compound (VCS) measurement, methyl mercaptan/hydrogen sulphide ratio by gas chromatography, organoleptic testing, tongue coating score, and periodontal parameters were evaluated in 823 patients complaining of oral malodour. Amongst these patients, 89 with oral pathogenic halitosis received tongue cleaning and periodontal therapy. Oral malodour and periodontal parameters were measured at baseline and after treatment. RESULTS: Amongst 823 patients, 102 were diagnosed with gingivitis and 721 with periodontitis. VCS levels and periodontal parameters increased according to the severity of oral malodour. Organoleptic testing significantly correlated with periodontal probing depth and a percentage of periodontal pocket depth ≥4mm (r=0.40 and 0.39 respectively). There were significant correlations between methyl mercaptan/hydrogen sulphide ratio and periodontal parameters. Significant decrease in oral malodour and periodontal parameters in 89 patients with oral pathogenic halitosis was also observed after periodontal treatment. CONCLUSIONS: Oral malodour is associated with periodontal disease, and periodontal therapy combined with tongue cleaning is beneficial for oral pathogenic halitosis.