Biosynthesis of 2-aminooctanoic acid and its use to terminally modify a lactoferricin B peptide derivative for improved antimicrobial activity

Terminal modification of peptides is frequently used to improve their hydrophobicity. While N-terminal modification with fatty acids (lipidation) has been reported previously, C-terminal lipidation is limited as it requires the use of linkers. Here we report the use of a biocatalyst for the production of an unnatural fatty amino acid, (S)-2-aminooctanoic acid (2-AOA) with enantiomeric excess gt 98% ee and the subsequent use of 2-AOA to modify and improve the activity of an antimicrobial peptide. A transaminase originating from Chromobacterium violaceum was employed with a conversion efficiency 52-80% depending on the ratio of amino group donor to acceptor. 2-AOA is a fatty acid with amino functionality, which allowed direct C- and N-terminal conjugation respectively to an antimicrobial peptide (AMP) derived from lactoferricin B. The antibacterial activity of the modified peptides was improved by up to 16-fold. Furthermore, minimal inhibitory concentrations (MIC) of C-terminally modified peptide were always lower than N-terminally conjugated peptides. The C-terminally modified peptide exhibited MIC values of 25 mu g/ml for Escherichia coli, 50 mu g/ml for Bacillus subtilis, 100 mu g/ml for Salmonella typhimurium, 200 mu g/ml for Pseudomonas aeruginosa and 400 mu g/ml for Staphylococcus aureus. The C-terminally modified peptide was the only peptide tested that showed complete inhibition of growth of S. aureus

Advanced glycation end products (AGEs) in diabetic complications

Hyperglycemic condition in diabetes accelerates formation of advanced glycation end products (AGEs) that are formed as a result of series of reaction between reducing sugars and proteins. Accumulation of AGEs has been implicated in development of insulin resistance as well as in the pathogenesis of diabetic complications. The principal mechanism by which AGEs render harmful effects is through interaction with cell bound receptors. Certain receptors like AGE-R1 are involved in degradation of AGEs, while certain other receptors like receptor for AGE (RAGE) bring about counter effects exacerbating the situation. Accumulation of diverse AGEs, synergistically down regulate AGE-R1 while up regulate RAGE causing vicious cycle leading to enhanced formation and further accumulation of AGEs. In this article we discuss the formation of heterogeneous AGEs, importance of detection and quantification of AGEs, biological degradation of AGEs via different receptors, AGE-RAGE and its role in proinflammatory signaling, AGE mediated diabetic vascular complications such as nephropathy, retinopathy, neuropathy, cardiovascular and cerebrovascular diseases and finally the biological inhibition of AGEs is discussed along with chemical inhibitors for AGEs and natural products in AGE inhibition as a measure for the prevention of diabetic complications