Metabolism and enzymology of cyanide/metallocyanide biodegradation by Fusarium solani under neutral and acidic conditions

A strain of Fusarium solani degrades metal-complexed cyanides under neutral and acidic pH conditions. Cyanide undergoes hydrolysis to formamide by cyanide hydratase (formamide hydrolyase, EC 4.2.1.66) which is in turn hydrolyzed to ammonia and formic acid by an amidase. The ammonia is their utilized for growth. Formic acid does not accumulate in the medium presumably rifle to its conversion to CO2 by formate dehydrogenase. Cyanide hydratase activity is induced by cyanide or metallocyanides under both acidic and neutral pH conditions, but not by ammonia or formamide; however, the fungus call utilize formamide as the source of nitrogen for growth. F. solani biotransforms K2Ni(CN)(4) and K4Fe(CN)(6) to ammonia under neutral and acidic pH conditions, respectively. The semipurified enzyme has optimal activity for KCN at pH 7.5 and has a K-m of 4.7 mM and a V-max of 1.7 mu mol min(-1) mg(-1) protein. Enzyme purification revealed that the native molecular weight of the enzyme is greater than 300 kDa due to its elution in the void volume during gel filtration, and comprises subunits with a molecular mass of approximately 45 kDa. The N-terminal sequence of the purified cyanide hydratase has a strong homology to previously purified cyanide hydratases, nitrilases, and a cyanidase enzyme. (C) 1998 Elsevier Science Inc.