Non-crosslinking advanced glycation end products affect prohormone processing

Biochem J. 2023 Dec 19:BCJ20230321. doi: 10.1042/BCJ20230321. Online ahead of print.ABSTRACTAdvanced glycation end products (AGEs) are non-enzymatic post-translational modifications of amino acids. and are associated with diabetic complications. One proposed pathomechanism is the impaired processing of AGE-modified proteins or peptides including prohormones. Two approaches were applied to investigate whether substrate modification with AGEs affects the processing of substrates like prohormones to the active hormones. First, we employed solid phase peptide synthesis to generate unmodified as well as AGE-modified protease substrates. Activity of proteases towards these substrates was quantified. Second, we tested the effect of AGE-modified proinsulin on the processing to insulin. Proteases showed the expected activity towards the unmodified peptide substrates containing arginine or lysine at the C-terminal cleavage site. Indeed, modification with Nε-carboxymethyllysine (CML) or methylglyoxal-hydroimidazolone 1 (MG-H1) affected all proteases tested. Cysteine cathepsins displayed a reduction in activity by around 50 % towards CML and MG-H1 modified substrates. The specific proteases trypsin, proprotein convertases subtilisin-kexin type proteases (PCSKs) and carboxypeptidase E (CPE) were completely inactive towards modified substrates. Proinsulin incubation with methylglyoxal at physiological concentrations for 24 h resulted in the formation of MG-modified proinsulin. The formati...
Source: The Biochemical Journal - Category: Biochemistry Authors: Source Type: research