Tannic acid effects on Raphanus raphanistrum root acid phosphatase

The effects of tannic acid (TA) on acid phosphatase (APase) (E.C.3.1.3.2) f rom root extracts of fertilized or unfertilized Raphanus raphanistrum plant s were examined. TA inhibited APase activity non-competitively; V-max was r educed, but the apparent K-m was unaffected in the presence of added TA. En dogenous tannin content ranged between 0.26 and 0.56 mu mole.g fresh weight (-1) of root tissue. Enzyme activity data was extrapolated to provide estim ates of activity in the absence of any TA; uncorrected APase activity of R raphanistrum was underestimated by an average of 25%. Addition of polyvinyl pyrrolidone (PVP) did not affect measured enzyme rates in a consistent mann er.