Recent advances in chemical genomics.

Chemical genomics, which utilizes specially designed small chemical compounds early in the discovery phase of new drugs to explore the life science at various levels, can address biological questions that are not amenable to genetic manipulation or functional genomics/proteomics approaches. Following the development of HT phenotypic assays and DNA expression analysis, the integration of cell-based assays with activity / affinity-based approaches allows us to interrogate the cells by analyzing phenotypic alterations, changes of transcript signature or detecting the differences in protein expression levels. Furthermore, activity / affinity-based techniques directly provide a druggable subset of gene products, which interact with small molecules, greatly reducing the complexity of analyzing the proteome. In this paper, we give an account of the recent advances (approaches and strategies) in the field of chemical genomics, and discuss how these approaches enable the investigator to obtain a novel therapeutically relevant target as well as drug candidates acting on them in a target-specific manner. This novel post-genomic discovery strategy, where target identification/ validation is carried out by interactions with small molecules, could significantly reduce the time-scale for early drug discovery, and increase the success rate of finding novel, druggable targets, as well as more specific drug candidates.

Distinct behavior of mutant triosephosphate isomerase in hemolysate and in isolated form: molecular basis of enzyme deficiency.

In a Hungarian family with severe decrease in triosephosphate isomerase (TPI) activity, 2 germ line-identical but phenotypically differing compound heterozygote brothers inherited 2 independent (Phe240Leu and Glu145stop codon) mutations. The kinetic, thermodynamic, and associative properties of the recombinant human wild-type and Phe240Leu mutant enzymes were compared with those of TPIs in normal and deficient erythrocyte hemolysates. The specific activity of the recombinant mutant enzyme relative to the wild type was much higher (30%) than expected from the activity (3%) measured in hemolysates. Enhanced attachment of mutant TPI to erythrocyte inside-out vesicles and to microtubules of brain cells was found when the binding was measured with TPIs in hemolysate. In contrast, there was no difference between the binding of the recombinant wild-type and Phe240Leu mutant enzymes. These findings suggest that the missense mutation by itself is not enough to explain the low catalytic activity and "stickiness" of mutant TPI observed in hemolysate. The activity of the mutant TPI is further reduced by its attachment to inside-out vesicles or microtubules. Comparative studies of the hemolysate from a British patient with Glu104Asp homozygosity and with the platelet lysates from the Hungarian family suggest that the microcompartmentation of TPI is not unique for the hemolysates from the Hungarian TPI-deficient brothers. The possible role of cellular components, other than the mutant enzymes, in the distinct behavior of TPI in isolated form versus in hemolysates from the compound heterozygotes and the simple heterozygote family members is discussed.