Distribution studies on polyglutamate forms of folate.

Abstract

this case was found to be 42.0s' (see above). The effects on other NADH diaphorase activities of arsenite treatment of reduced enzyme are shown in Table 1. In direct contrast with its effects on oxidized enzyme (Fig. l), is the marked inhibition of NADHdichlorophenol-indophenol activity accompanying arsenite treatment of NADHreduced enzyme. This could be due to the exposure on reduction of a second site with which arsenite may interact (Rajagopalan &Handler, 1967). However, in agreement with the data of Fig. 1 (b), arsenite treatment of reduced-cyanide-inactivated enzyme failed to alter activity significantly (Table 1). Thus we suggest that pre-reduction merely alters the mode of binding of arsenite to the active-centre persulphide groups. The effects of arsenite on the NADH diaphorase activity of oxidized or reduced enzyme clearly depend on the integrity of the molybdenum-centre persulphide groups and are restricted to activity with dichlorophenol-indophenol and trinitrobenzene sulphonate as electron acceptors. This, in our view, infers that these two acceptors also interact with the molybdenum centres of these enzymes.