Abstract
Dipeptide syntheses starting from Ac-L-Tyr-OEt or Z-L-X-OMe (X: Asp, Tyr, Phe, Arg, Lys or Thr) and glycine amide in biphasic reaction media were achieved using two commercially available porcine pancreatic lipase (PPL) preparations (crude (cPPL) and purified PPL (pPPL)). Under the mild conditions employed, α-chymotrypsin, a pancreatic protease that also presents esterase activity, catalyzed Ac-L-Tyr-Gly-NH2 synthesis with high productivity. Product hydrolysis also occurred in most of the syntheses studied. Polyacrylamide gel electrophoresis, enzymatic assays employing specific chromogenic substrates and size-exclusion chromatography revealed that cPPL and pPPL contain contaminant proteases and, therefore, exhibit esterase and amidase activities. Overall, these data indicate that those contaminants may be the main catalysts of peptide bond synthesis when Nα-blocked-L-amino acid esters and the commercial PPL preparations are used. On the other hand, such data do not contest the possibility of using such enzyme preparations as an inexpensive source of catalysts for dipeptide synthesis under soft conditions.
Highlights
IntroductionInterest in environment friendly technologies has increased drastically
In the last decade, interest in environment friendly technologies has increased drastically
It is noteworthy that the couplings already studied present the following characteristics: (i) they are medium- or long-term reactions; (ii) almost all involve soluble substrates in monophasic media; (iii) they occur under a wide variety of experimental conditions, hampering comparisons; iv) the majority employ crude porcine pancreatic lipase (PPL), which is surprising because it has been claimed that this is a mixture of enzymes (PPL and contaminant proteases).[20,21,29]
Summary
Interest in environment friendly technologies has increased drastically. The ability of enzymes to catalyze reactions required for the manufacture of fine chemicals has been explored extensively.[1]. Vol 19, No 8, 2008 mediate the hydrolysis of triacylglycerides into mono, diacylglycerides, fatty acids and glycerol through the formation of an acyl-enzyme intermediate followed by deacylation with water.[15] it has been reported the use of commercial lipases in peptide bond syntheses starting from Nα-blocked-amino acid esters (acyl donors) and amino acid or peptide amides (acyl acceptors).[16,17,18,19] many authors have claimed that these enzyme preparations present amidase activity, due to contaminant proteases.[20,21] they could lead to the undesired hydrolysis of the product formed
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