Crystallographic Studies of Chicken Triose Phosphate Isomerase

Abstract

One of the simplest reactions in the glycolytic pathway is the interconversion of dihydroxy acetone phosphate (DHAP) and d-glyceraldehyde-3-phosphate (GAP) which is catalyzed by triose phosphate isomerase (E.C. 5.3.1.1), TIM. The equilibrium of the reaction (Keq = 420 at 20°C, Reynolds et al., 1971) is strongly in favor of DHAP, so the complex of TIM with this substrate might be expected to be observable crystallographically. In conjunction with progress in the crystallographic structure determination of the native enzyme, studies of the complex of TIM with DHAP are being undertaken. Preliminary results show that direct observation of the interactions between enzyme and substrate in the crystal is complicated by changes in the molecular packing, but knowledge of the structure of the native enzyme will help interpret these results. TIM presents a system which offers a hitherto unequalled opportunity of studying the interaction of an enzyme with its true substrate at the...