Glyoxalase system

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The glyoxalase system is a set of enzymes that carry out the detoxification of methylglyoxal and the other reactive aldehydes that are produced as a normal part of metabolism.[1] This system has been studied in both bacteria and eukaryotes.[2][3]

This detoxification is accomplished by the sequential action of two thiol-dependent enzymes; firstly glyoxalase І, which catalyses the isomerisation of the spontaneously formed hemithioacetal adduct between GSH and 2-oxoaldehydes (such as methylglyoxal) into S-2-hydroxyacylglutathione.[4][5] Secondly, glyoxalase ІІ hydrolyses these thiolesters and in the case of methylglyoxal catabolism, produces D-lactate and GSH from S-D-lactoyl-glutathione.[6]

This system shows many of the typical features of the enzymes that dispose of endogenous toxins. Firstly, in contrast to the amazing substrate range of many of the enzymes involved in xenobiotic metabolism, it shows a narrow substrate specificity. Secondly, intracellular thiols are required as part of its enzymatic mechanism and thirdly, the system acts to recycle reactive metabolites back to a form which may be useful to cellular metabolism.

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  1. ^ Vander Jagt, D. (1989). The glyoxalase system. In Glutathione: Chemical, Biochemical and Medical Aspects. Part A, D. Dolphin, R. Poulson, and O. Avramovic, eds. (New York: John Wiley & Sons), pp. 597-641.
  2. ^ Dixon DP, Cummins L, Cole DJ, Edwards R (1998). "Glutathione-mediated detoxification systems in plants". Curr. Opin. Plant Biol. 1 (3): 258–66. doi:10.1016/S1369-5266(98)80114-3. PMID 10066594. 
  3. ^ Inoue Y, Kimura A (1995). "Methylglyoxal and regulation of its metabolism in microorganisms". Adv. Microb. Physiol. 37: 177–227. doi:10.1016/S0065-2911(08)60146-0. PMID 8540421. 
  4. ^ Thornalley PJ (2003). "Glyoxalase I--structure, function and a critical role in the enzymatic defence against glycation". Biochem. Soc. Trans. 31 (Pt 6): 1343–8. doi:10.1042/BST0311343. PMID 14641060. 
  5. ^ Creighton DJ, Hamilton DS (2001). "Brief history of glyoxalase I and what we have learned about metal ion-dependent, enzyme-catalyzed isomerizations". Arch. Biochem. Biophys. 387 (1): 1–10. doi:10.1006/abbi.2000.2253. PMID 11368170. 
  6. ^ Vander Jagt DL (1993). "Glyoxalase II: molecular characteristics, kinetics and mechanism". Biochem. Soc. Trans. 21 (2): 522–7. PMID 8359524.