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The oxidation of dihydroorotate and the reduction of fumarate by dihydroorotate dehydrogenase from Trypanosoma cruzi (TcDHOD) are investigated to observe the crystal structures of (TcDHOD) in the ligand free and complex forms. There is found to be coupling of the FMN reduction with oxidation reaction which facilitates the reduction of fumarate to succinate.

The structures of the cytochrome b(sub 6)f complex obtained from the thermophilic cyanobacterium Mastigocladus laminosus and the green alga Chlamydomonas reinhardtii are analyzed. The transfer of protons across the b(sub 6)f complex, utilizing oxidation and reduction of lipophilic quinone, establishes a proton electrochemical potential gradient that is negative on the stromal side of the membrane and positive on the lumen side.

The crystal structure analyses of the catalytic site mutant of beta-amylase from Bacillus cereus var. mycoides along with the substrae maltopentaose and the wild-type enzyme complexed with maltose at 2.1 and 2.0 angstroms, respectively, are presented. Continuous density corresponding to maltopentaose substrae in the active site of the catalytic site mutant of beta-amylase indicates that the substrate is not hydrolyzed.