Kinetic and thermodynamic control of the relative yield of the deamidationof asparagine and isomerization of aspartic acid residues

Selective deamidation of Asn(67) of RNase A to beta -Asp(67) and Asp(67) re sidues at neutral pH initially produces greater amounts of the beta -Asp de rivative. As the reaction proceeds the relative concentration of [Asp(67)]- RNase A increases and, at equilibrium, becomes predominant. Such a discrepa ncy between the kinetic and thermodynamic control on reaction products is d iscussed in light of information from X-ray three-dimensional analysis and the lower thermodynamic stability of the beta -Asp derivative relative to t he parent enzyme.