title: Stereoselective reactivity of the SH groups of yeast glyceraldehydephosphate dehydrogenase in the allosteric T and R states.
abstract: Yeast glyceraldehyde-3-phosphate dehydrogenase as a typical SH enzyme is inactivated by the antipodes of a-iodopropionic acid and its amide at different rates. The apoenzyme reacts faster with the D(+) antipode of the free a-iodopropionic acid (k(D)/k(L) = 6.8) and the L(-) antipode of the amide (k(L)/k(D) = 3). On addition of NAD(+) the stereoselectivity of the SH group towards a-iodopropionic acid is inverted, that towards the amide is enlarged, the rate relationships depending on the NAD(+) concentration.The results were interpreted by the assumption, that the allosteric T state of the enzyme reacts most rapidly with the D(+) antipodes, whereas the R state favours the L(-) antipodes of the alkylation reagents. The dependence of the reaction rates on the NAD(+) concentration could be fitted to the allosteric function of state R.
authors.affiliation: Chemisches Laboratorium der Universität Freiburg/Br., Switzerland
authors.forename: B
authors.initials: B
authors.lastname: Eisele
authors.forename: K
authors.initials: K
authors.lastname: Wallenfels