Enzymatic Amine Acyl Exchange in Peptides on Gold Surfaces

Abstract

Reversible as well as stereo- and chemoselective: various proteases such as thermolysin and chymotrypsin catalyze amine acyl exchange in peptides. This acyl exchange can be used to modify amino-functionalized surfaces under physiological reaction conditions and provides an alternative mechanism for posttranslational transpeptidation reactions such as peptide-splicing reactions in the proteasome.

An Enzymatic N‐Acylation Step Enables the Biocatalytic Synthesis of Unnatural Sialosides

“…[7] A more attractive strategy is the reversible enzymatic amine acyl exchange of amines and free carboxylic acids (Scheme 1; compound 2 to 3 using free acid as the acylating agent), thus directly replacing the chemical step. Such reactions, with more reactive (protonated) carboxylic acids stabilized in the active sites of enzymes, have been previously described for N-acylation reactions of peptides, urea, or ammonia, [8] but to the best of our knowledge, there is no example of the Nacylation of glucosamine. An enzyme-catalyzed approach would not require activation of the carboxylate and in addition has the potential to be highly selective for glucosamine in the presence of other biogenic amines.…”

Application of Biocatalysis to on‐DNA Carbohydrate Library Synthesis

“…[9,10] Given the complexity of carbohydrate structure and the need for highly selective transformations, carbohydrate-basedt arget libraries are an excellent test for the application of biocatalysis to synthesis of DNA-encoded ligand libraries. [15][16][17][18][19] The overall strategy to accessalibrary of DNA-carbohydrate glycoconjugates by using ac ombination of chemical methods and biocatalysis is outlined in Scheme1.T he initial step involvesc hemical ligation of the first carbohydrate building block,f ollowed by biocatalytic transformationt oe ither elongate the glycan structure by glycosylationo rg enerate an aldehyde by oxidation of the primary sugar hydroxyl groupsf or the site-specific modification of the carbohydrate by reductive amination or hydrazone ligation. [12] Given the lack of precedent, we decided to study biocatalysts that had previously been shown to tolerate diverse conjugates and focus on glycosylationr eactions catalyzed by glycosyltransferases [13] and selectivef unctionalization of carbohydrates.…”

“…To this end, we carried out reductive amination on glycoconjugates bearing an aldehyde according to ap rocedure reported recently fort he synthesis of DNA-encoded chemical libraries. Further,w ee valuated the coupling efficiency of various amines containing specific chemical functionalities (Table S2, entries [17][18][19], such as alkyne (52), alkene (53), and alcohol( 54). Importantly,r eaction monitoring by MALDI-ToF indicated that decreasing the amount of amine or reducing agent prevented the reaction from reaching optimum conversion (data not shown).…”

“…Finally,t he coupling of benzylamineb yr eductive amination to aldehydes from DNA-bGlc (18), DNA-bLac (19), DNA-bGlcNAc ( 20), DNA-bGalNAc (21), and DNA-bLacNAc (23; Scheme 3) was investigated. The anticipated products (55-60) were obtained with conversion rates from 36 to 92 % (Table S3), which were in accordance with those previously observed when using the hydrazone procedure (Table 1), demonstratingt hat both reactions were equallye fficient.…”

“…[14] In previousw ork, our group and others developed such enzymatic processes for glycoconjugate synthesis, including syntheses of glycolipids, glycoproteins, and glycansc onjugated to surfaces. [15][16][17][18][19] The overall strategy to accessalibrary of DNA-carbohydrate glycoconjugates by using ac ombination of chemical methods and biocatalysis is outlined in Scheme1.T he initial step involvesc hemical ligation of the first carbohydrate building block,f ollowed by biocatalytic transformationt oe ither elongate the glycan structure by glycosylationo rg enerate an aldehyde by oxidation of the primary sugar hydroxyl groupsf or the site-specific modification of the carbohydrate by reductive amination or hydrazone ligation. Both chemical and biocatalytic transformations were monitored by MALDI-ToF mass spec-trometry,w hich allowed us to determinet he chemical identity of the glycoconjugates generated.…”