Nε-(prop-2-ynyloxycarbonyl)-L-lysine hydrochloride

Background: Advanced glycation end products (AGEs) are pathogenic factors of diabetic nephropathy (DN), causing renal damage in various ways. The aim of this study is to investigate the ectopic lipid accumulation caused by AGEs in human renal tubular epithelial cell line (HK-2) cells and the kidney of type 2 diabetic rats. Methods: In vivo study, diabetes was induced in male Sprague-Dawley rats through intraperitoneal injection of high-fat/high-sucrose diet and low-dose streptozocin (STZ). Two weeks after STZ injection, the diabetic rats were randomly divided into two groups, namely, untreated diabetic and Aminoguanidine Hydrochloride (AG, an AGEs formation inhibitor)-treated (100 mg/Kg/day, i.g., for 8 weeks) group. In vitro study, according to the different treatments, HK-2 were divided into 6 groups. Intracellular cholesterol content was assessed by Oil Red O staining and cholesterol enzymatic assay. Expression of mRNA and protein of molecules controlling cholesterol homeostasis in the treated cells was examined by real-time quantitative PCR and western blotting, respectively. SREBP cleavage-activating protein (SCAP) translocation was detected by confocal microscopy. Results: Here we found Nε-(carboxymethyl) lysine (CML, a member of the AGEs family) increased Oil Red O staining and intracellular cholesterol ester (CE) in HK-2 cells; Anti-RAGE (AGEs receptor) reduced lipid droplets and the CE level. A strong staining of Oil Red O was also found in the renal tubules of the diabetic rats, which could be alleviated by AG. CML upregulated both mRNA and protein expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoAR), LDL receptor (LDLr), sterol regulatory element binding protein-2 (SREBP-2) and SCAP, which were inhibited by anti-RAGE. The upregulation of these molecules in the kidney of the diabetic rats was also ameliorated by AG. Furthermore, AG reduced serum and renal CML deposition, and improved urine protein and u-NGAL in type 2 diabetic rats. Conclusions: Overall, these results suggest that CML caused DN might be via disturbing the intracellular feedback regulation of cholesterol. Inhibition of CML-induced lipid accumulation might be a potential renoprotective role in the progression of DN.

Aldoses and ketoses can glycate proteins yielding isomeric Amadori and Heyns products, respectively. Evidently, D-fructose is more involved in glycoxidation than D-glucose favoring the formation of advanced glycation endproducts (AGEs). While Amadori products and glucation have been studied extensively, the in vivo effects of fructation are largely unknown. The characterization of isomeric Amadori and Heyns peptides requires sufficient quantities of pure peptides. Thus, the glycated building block Nα-Fmoc-Lys[Nε-(2-deoxy-D-glucos-2-yl),Nε-Boc]-OH (Fmoc-Lys(Glc,Boc)-OH), which was synthesized in two steps starting from unprotected D-fructose and Fmoc-L-lysine hydrochloride, was site-specifically incorporated during solid-phase peptide synthesis. The building block allowed the synthesis of a peptide identified in tryptic digests of human serum albumin containing the reported glycation site at Lys233. The structure of the glycated amino acid derivatives and the peptide was confirmed by mass spectrometry and NMR spectroscopy. Importantly, the unprotected sugar moiety showed neither notable epimerization nor undesired side reactions during peptide elongation, allowing the incorporation of epimerically pure glucosyllysine. Upon acidic treatment, the building block as well as the resin-bound peptide formed one major byproduct due to incomplete Boc-deprotection, which was well separated by reversed-phase chromatography. Expectedly, the tandem mass spectra of the fructated amino acid and peptide were dominated by signals indicating neutral losses of 18, 36, 54, 84 and 96 m/z-units generating pyrylium and furylium ions.

epsilon-Lysine acylase from Streptomyces mobaraensis (Sm-ELA), which specifically catalyzes hydrolysis of the epsilon-amide bond in various Nepsilon-acyl-L-lysines, was cloned and sequenced. The Sm-ELA gene consists of a 1617-bp open reading frame that encodes a 538-amino acid protein with a molecular mass of 55,816Da. An NCBI protein-protein BLAST search revealed that the enzyme belongs to the YtcJ-like metal-dependent amidohydrolase family, which is further characterized as the metallo-dependent hydrolase superfamily. The Sm-ELA gene was ligated into a pUC702 vector for expression in Streptomyces lividans TK24. Expression of recombinant Sm-ELA in S. lividans was approximately 300-fold higher than that in wild-type S. mobaraensis. The recombinant Sm-ELAs from the cell-free extract and culture supernatant were purified to homogeneity. The specific activities of the purified Sm-ELAs were 2500-2800U/mg, which were similar to that obtained for the wild-type Sm-ELA. Using the cell-free extract of the recombinant S. lividans cells, Nepsilon-lauroyl-L-lysine was synthesized from 500mM L-lysine hydrochloride and 50, 100, or 250mM lauric acid in an aqueous buffer solution at 37 degrees C. The yields were close to 100% after 6 and 9h of reaction for 50 and 100mM lauric acid, respectively, and 90% after 24h for 250mM lauric acid.