A POTENTIAL PROTEIN ENGINEERING SITE IN ASPERGILLUS-NIGER GLUCOAMYLASE - VICINITY OF DISULFIDE BRIDGE 449-222

Thermal denaturation and kinetic studies have been performed on glucoa mylase and on its truncated forms obtained by papain proteolysis. Subs trates of differing length had significant effect neither on stability of the enzyme forms nor on proteolytic susceptibility of the native e nzyme. Formation of disulphide-bridged oligomers seems to be on the de naturation pathway but it is not the rate-determining step in irrevers ible inactivation. Results indicate that stabilization around the acce ssible disulphide of the protein might retard thermodenaturation but n ot catalysis.