INFLUENCE OF 1,10-PHENANTHROLINE AND ITS ANALOGS, OTHER CHELATORS ANDTRANSITION-METAL IONS ON DIPEPTIDASE ACTIVITY OF THE RUMEN BACTERIUM,PREVOTELLA-RUMINICOLA

Prevotella ruminicola plays a prominent role in the breakdown of pepti des in the rumen, a process which contributes to excessive ammonia pro duction and inefficient nitrogen retention in ruminants. Various metal ions and chelators were examined to assess how the metal ion-dependen t dipeptidase activity of P. ruminicola M384 might be inhibited. Using sonicated extracts, Cu2+, Cr2+ and Hg2+ were most inhibitory, decreas ing Ala, breakdown to 15, 15 and 5% of control activity, whereas Co2+, Mn2+ and Zn2+ stimulated activity by 189, 30 and 26%, respectively. T he chelators, EDTA, EGTA, TPEN and 1,10-phenanthroline, were inhibitor y, as were several phenanthroline analogues. Among the stereoisomers o f 1,10-phenanthroline tested, derivatives methylated on C-2 and C-9 we re less effective than the parent molecule, but 3,4,7,8-tetramethyl-1, 10-phenanthroline (TMP) was more inhibitory. Titration of the most eff ective inhibitors showed that EDTA, TPEN and TMP had similar potency a nd were effective at 0.1 mmol l(-1) and above. Thus some metal ions an d chelators are potent inhibitors of P. ruminicola dipeptidase, althou gh they are unlikely to be sufficiently specific to peptide metabolism to be useful in vivo.