Cyanide-metabolizing enzyme rhodanese in human tissues: comparison with domestic animals

Abstract

The enzyme rhodanese (thiosulfate:cyanide sulfurtransferase) is an ubiquitous enzyme with activity in all living organisms, from bacteria to man. It has been suggested that this enzyme plays a central role in cyanide detoxification. The purpose of this investigation was to determine rhodanese activities in different tissues of human and compare them with those found in domestic animals. Normal human tissues were obtained from consenting patients who had undergone surgery after confirmation of nonneoplastic condition. Tissue extracts were prepared from liquid nitrogen-frozen samples and rhodanese specific activity and activity per gram tissue was measured by determination of enzymatically formed thiocyanate. The highest activity of rhodanese was found in kidney, followed by liver, brain, lung, muscle, and stomach. Other tissues studied did not show significant rhodanese activity. The results obtained in this study were compared with previously reported information on domestic animals. Human liver contains lower rhodanese activity compared with ruminants and nonruminants, except for dog which has comparable hepatic activity with human. Human kidney contains significant activity and the value is higher than those of camels, pigs, dogs, and chickens and is comparable with those of goats. The results of this study might indicate the involvement of rhodanese in cyanide detoxification in tissues which might be more exposed to cyanide due to higher blood supply to these tissues. On the other hand, rhodanese might perform other functions in human organs which are specific to these tissues.