2-Keto-3-deoxy-6-phosphogluconate formation

M. C. Shelton, I. C. Cotterill, S. T. A. Novak, R. M. Poonawala, S. Sudarshan, and E. J. Toone, 2-Keto-3-deoxy-6-phosphogluconate aldolases as catalysts for stereocon-trolled carbon-carbon bond formation, J. Am. Chem. Soc., 118 (1996) 2117-2125. 

Figure 9.80 Representative chromatographs of Entner-Doudoroff metabolites, (a) 6-Phosphogluconate dehydratase-catalyzed formation of 2-keto-3-deoxy-6-phosphogluconate (12.51 min). (b) Blank run for 6-phosphogluconate dehydratase-catalyzed formation of 2-keto-3-deoxy-6-phosphogluconate, (KDPG) 6-phosphogluconate omitted from assay. (From Taha and Deits, 1994.)...

As mentioned, the mildness of NaBHaCN (coupled with its effectiveness and stability in aqueous media) has attracted considerable interest for applications in biochemical areas. Examples include the trapping of suspected imine intermediates produced in enzyme (mitochondrial monoamine oxidase) inactivation by amines, the establishment by reduction of the positions of imine-forming amines in 2-keto-3-deoxy-6-phosphogluconate aldolase, and the transfer labeling of methionyl-tRNA synthetase and methionyl-tRNA transformalase by treatment with periodate-treated tRNA. In fact, most biochemical applications of NaBHaCN have utilized in situ imine formation-reduction (i.e. reductive amination) conditions and will be further discussed in Section 1.2.2.3.1. 

Another example of deviant biochemistry in protozoa is the utilization, by Entamoeba histolytica, of pyrophosphate in place of the usual ATP, as a coenzyme for phosphofructokinase (Beeves, Serrano and South, 1976). The major path of glucose utilization in this parasite is formation of pyruvate from phospho-gluconate and from 2-keto-3-deoxy-6-phosphogluconate (Florkin and Mason, 1960). 

Formation of a carbinolamine as the short-lived Schiff base precursor (C) could be trapped by Hash freezing of 2-keto-3-deoxy-6-phosphogluconate aldolase in the presence of its natural donor substrate pyruvate [46]. Stereospecificity of the reaction seems to be ensured mostly by hydrophobic contact of the pyruvate methyl group in the active site. 

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