Cytosol nonspecific dipeptidases

Increased permeability is just one prerequisite in the development of useful peptide prodrugs. Another condition is that efficient bioactivation must follow absorption. Mucosal cell enzymes able to hydrolyze peptides include exopeptidases such as aminopeptidases and carboxypeptidases, endopepti-dases, and dipeptidases such as cytosolic nonspecific dipeptidase (EC 3.4.13.18), Pro-X dipeptidase (prolinase, EC 3.4.13.4), and X-Pro dipeptidase (prolidase, EC 3.4.13.9). For example, L-a-methyldopa-Pro was shown to be a good substrate for both the peptide transporter and prolidase. This dual affinity is not shared by all dipeptide derivatives, and, indeed, dipeptides that lack an N-terminal a-amino group are substrates for the peptide transporter but not for prolidase [29] [33] [34],... 

There are many dipeptidases [EC 3.4.13.x]. Cytosol nonspecific dipeptidase [EC 3.4.13.18] (also referred to as peptidase A, glycylglycine dipeptidase, glycylleucine dipeptidase, and A -)3-alanylarginine dipeptidase) catalyzes the hydrolysis of dipeptides. Membrane dipeptidase [EC 3.1.13.19] (also known as microsomal dipeptidase, renal dipeptidase, and dehydropeptidase I) is a zinc-dependent enzyme (a member of the peptidase family M19) that also catalyzes the hydrolysis of dipeptides. 

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