| The affinity of phosvitin with serine hydroxymethyl transferase ( SHMT ) , an acidic multi subunit protein , was evaluated by measurements of enzyme activity , sedimentation velocity , steady state fluorescence , circular dichroism and kinetic thermal stability . ^^^ While the presence of phosvitin had no effect on the SHMT activity , the sedimentation coefficient of SHMT increased from 8 . 7 S to 12 . 5 S suggesting the formation of a complex at a SHMT : phosvitin molar ratio of 2 : 1 . ^^^ Based on steady state fluorescence quenching measurements an association constant of 2 . 4 + / 0 . 2 10 10 ( 5 ) M 1 at 25 degrees C was obtained for the interaction of phosvitin with SHMT . ^^^ |