Enzymes are the factories of biological cells that drive most of the biochemical transformations necessary for living. These macromolecules evolved over billions of years to optimize their function to perform a vast range of chemical transformations. They represent some of the fastest and most selective catalysts known to us. In order to engineer enzymes and utilize their potential for new reactions, first we need to understand their native functions. Structural enzymology uses primarily x-ray crystallographic methods to observe enzymes at atomic scale.Rice granule-bound starch synthase I (GBSSI) and rice branching enzyme I (BEI) are two key components of starch biosynthesis. Using structural enzymology and kinetic studies, an enhanced model of their biochemical function is generated. In the case of GBSSI, new structures with its native substrate were obtained and also for the first time its open conformer structure was solved. Developing kinetic experiments for rice BEI and investigating the structure of rBEI- maltododecaose complex revealed the binding site for the donor and acceptor chains.Cg10062, a member of the tautomerase superfamily, transforms propiolate by hydration and decarboxylation. Intermediate-bound structures of various Cg10062 variants, identified many intermediates in the reaction. A mechanistic model is developed, and behavior of its mutants is clarified.
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