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Research has been conducted on the Stereum purpureum endopolygalacturonase. The crystal structures of this endopolygalacturonase have been investigated in the native and galacturonic acid complex states at atomic resolution and the results indicate that the galacturonate molecules have been observed at +1 and -1 subsites.

The crystal structure of tropinone reductase-II (TR-II) from Datura starmonium complexed with NADP+ and pseudotropine is investigated at 1.9 Angstrom resolution. The structure reveals the active site architecture of TR-II and the structure of the bound substrates. Results also show that the alphaG', a part of the active site that is flexible in the unliganded TR-II, is an ordered structure in the TR-II ternary complex. These findings suggest that the active site is properly arranged for catalytic reaction after the substrates bind.

A loopless mutant, with its loop replaced by three residues of glycine, is synthesized to study the function of the loop in Escherichia coli. The loopless mutant enzyme is similar to the wild type enzyme in the crystal structure. The loop replacement enhances the kinetic values of the glycine, which is involved in the loop replacement.

Adenosine(5')polyphospho(5')pyridoxals (APn-PLs; n = 2, 3, 4) were examined for affinity labeling of glutathione synthetase from Escherichia coli B. It was found that AP4-PL has the highest affinity and labels Lys-18 specifically. X-ray diffraction analysis of AP4-PL-soaked crystal has revealed binding of its adenosine moiety in the active-site crevice where the adenosine moiety of ATP binds. Thus, the adenosine moiety of AP4-PL binds at the nucleotide-binding site of the enzyme.

The flexible loop of glutathione synthetase in Escherichia coli B was studied through limited proteolysis and kinetic measurements for the wild type and mutant enzymes. Protein fragmentation and enzyme inactivation was seen as the peptide bond on position arginine 233 and glycine 234of the enzyme was disrupted. Stability of the loop is provided by the presence of substrates in the presence of proteases which is more evident in the wild-type enzyme although glycine did not show any protective effects. The findings suggest the role of the loop as binding site for substrate and its protective function for enzyme stability and activity.

A study is conducted which determines the crystal structures of maize pyruvate phosphate dikinase (PPDK) with and without phosphoenolpyruvate (PEP) at 2.3 angstrom resolution. By comparing the maize PPDK structures with and without PEP, the mode of binding of PEP to the C-terminal domain and the induced conformational changes in the central domain are elucidated.

Crystal structure analyses of the enzyme-substrate complexes of the tropinone reductase-II-NADPH and tropinone reductase-II-NADPH-tropinone complexes, prior to reaction initiation, reveal that the substrate tropinone is rotated relative to the product such that the active site is spatially organized for the reaction to proceed. Data indicate that side chains of the active site amino acid residues alter their conformation to facilitate the rotational movement.