Gene-enzyme structural relationship

Lederberg, J. (1956), Comments on the gene-enzyme relationship , in Gaebler, O. H. (Ed.), Enzymes Units of Biological Structure and Function, Academic Press, New York, pp. 161 -169. 

The structural relationship of tomatinase from B. cinerea to other tomatinases is unknown, but its molecular mass (70 kDa) is different from the other two enzymes mentioned before, 50 kDa from F. oxysporum [35, 38] and 110 kDa from S. lycopersici [33]. Moreover, when Quidde et al., attempted cloning of the tomatinase gene from B. cinerea using the tomatinase from S. lycopersici as a probe, they isolated a gene with high sequence homology, whose product had not tomatinase activity but was able to detoxify avenacin A-l [97], the saponin from oats related to some extent to tomatine. 

Directed evolution is a powerful tool used to improve lipase properties that does not depend on a comprehensive understanding of the relationship between enzyme structure and function. It rather depends on simple, yet powerfnl, random mutation and selection. The targeted genes are exposed to iterative cycles of random mutagenesis, expressed in an appropriate host and subsequently screened (Johannes and Zhao, 2006). Bacillus lipase was engineered by directed evolntion, where a lip gene was cloned and expressed in E. coli. The mutagenesis was executed by error-prone polymerase chain reaction (PCR). The mutation enhanced the specific activity of the lipase by twofold (Khurana et al., 2011). 

THE SEARCH FOR THE STRUCTURAL RELATIONSHIP BETWEEN GENE AND ENZYME... 

Based on these mechanisms a new frontier in the application of enzymes to biotechnology, including the development of synthetic enzymes (synzymes)82,83 will be exploited. Research on structure-function relationships between ribozymes and abzymes will lead to the development of a number of sequence specific catalysts, which will control expression of a specific gene or its products, and eventually to application as pathogen controls in agriculture and to clinical use. Sequence specific abzymes may also facilitate research on the primary structure determination of protein. 

The bird lysozymes c, of which chicken egg white lysozyme (CL) is the most extensively studied example, provide an ideal system to recreate evolutionary intermediates and to study structure-function relationships of reconstructed ancestral proteins. Three major considerations qualify the avian lysozyme system for reconstruction of evolutionary pathways (1) the biochemistry of the enzymes has been extensively studied and well characterized,3,4 (2) there are many natural variants available from other birds, and homologous comparisons can be ensured since lysozymes for all game birds are encoded by a single gene,5 and (3) the three-dimensional structure of CL has been resolved at the atomic level, which allows for structural interpretation of the mutational impact.2,4 Proteins representing the ancestral, evolutionarily intermediate, and derived states of chicken and related bird lysozymes are made and characterized as described below. 

Wales, M E, Wild J R (1991) Analysis of structure-function relationships by formation of chimeric enzymes produced by gene fusion, Methods in Enzymology, 202 687-706. 

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