Using citrate buffer (pH ) containing mML-cysteine, homodimeric starch phosphorylase from Corynebacterium calluane(CcStP) was dissociated into native-like folded subunits concomitant with release of pyridoxal 5¢-phosphate and loss of activity. The inactivation rate of CcStP under resolution conditions at 30 Cwas, respectively, four- and threefold reduced in two mutants, Arg234fiAla and Arg242fiAla, previously shown to cause thermostabilization of CcStP [Griessler, R., Schwarz, A., Mucha, J.&Nidetzky, B. .
