Dipeptidase glutathione

An exopeptidase that can only degrade a dipeptide. Examples are carnosine dipeptidase I (MEROPS M20.006), which degrades carnosine (beta-Ala-His), and membrane dipeptidase (MEROPS Ml9.001), which is important in the catabolism of glutathione, degrading the dipeptides Cys-Gly. Dipeptidases are included in Enzyme Nomenclature sub-subclass 3.4.13. 

Cilastatin prevents the metabolism of imipenem by renal tubular dipeptidase, which also hydrolyses the glutathione metabolite cysteinylglycine. In patients taking imipenem + cilastatin, plasma concentrations of cysteinylglycine were significantly increased, while cysteine concentrations fell and homocysteine concentrations were unchanged (483). The clinical significance of this is not clear. 

Glutathione, y-glutamyl derivatives, and (3-lyase substrates have been investigated as renal-specific prodrugs based on the presence of certain transporters such as plasma membrane transport systems for glutathione [28] and cysteine [29] conjugates and/or enzymes such as y-glutamyltrans-ferase (EC 2.3.2.2), dipeptidase, and p-lyase (EC4.4.1.13). 

Figure 9 Handling of 6-PG in renal proximal tubular cells. Abbreviations BBM, brush border plasma membrane BLM, basolateral plasma membrane 6-MP, 6-mercaptopurine 6-PG, S-(6-purinyl) glutathione 6-PC, S-(6-purinyl)-L-cysteine NAcPC, w-acetyl-S-(6-purinyl)-L-cysteine GGT, y-glutamyltransferase DP, dipeptidase P-lyase, cysteine conjugate P-lyase PLP, pyridoxal phosphate XO, xanthine oxidase 6-ThXan, 6-thioxanthine 6-ThUrate, 6-thiourate AOAA, aminooxyacetic acid and Av /, membrane potential. (Adapted from Ref. 30.)...

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