Immobilization and bioimprinting strategies to enhance the performance in organic medium of the metagenomic lipase LipC12

The present work evaluates the immobilization of LipC12 on different supports in tandem with bioimprinting technique, in order to improve its activity and stability in organic medium. Oleic acid was selected as the bioimprinting molecule. The immobilized LipC12 was applied in the synthesis of pentyl oleate by esterification reaction and in the production of fatty acids, mono, and diglycerides via hydrolysis of triacylglycerols, in n-heptane reaction media. For all immobilized lipase preparations, an increase in the conversion of oleic acid to pentyl oleate was observed when immobilization in tandem with bioimprinting treatment was carried out versus immobilization without bioimprinting. The highest conversions were achieved using LipC12 immobilized on hydrophobic supports. The reuse potential of the immobilized preparations was evaluated. The preparations were used in eight successive cycles of esterification reactions and the best results were obtained for LipC12 immobilized on Immobead 150 and chitosan. The activity for the hydrolysis of soybean oil was improved by bioimprinting treatment only for LipC12 immobilized on commercial polypropylene and Accurel MP-1000. LipC12 immobilized on hydrophilic supports or on Immobead150 could be used to hydrolyze tricaprylin to obtain diglycerides with a high proportion of 1,2-diglycerides in reaction times as short as 30 min.

Chemical Modification of Novel Glycosidases from Lactobacillus plantarum Using Hyaluronic Acid: Effects on High Specificity against 6-Phosphate Glucopyranoside

Three novel glycosidases produced from Lactobacillus plantarum, so called Lp_0440, Lp_2777, and Lp_3525, were isolated and overexpressed on Escherichia coli containing a His-tag for specific purification. Their specific activity was evaluated against the hydrolysis of p-nitrophenylglycosides and p-nitrophenyl-6-phosphate glycosides (glucose and galactose) at pH 7. All three were modified with hyaluronic acid (HA) following two strategies: A simple coating by direct incubation at alkaline pH or direct chemical modification at pH 6.8 through preactivation of HA with carbodiimide (EDC) and N-hydroxysuccinimide (NHS) at pH 4.8. The modifications exhibited important effect on enzyme activity and specificity against different glycopyranosides in the three cases. Physical modification showed a radical decrease in specific activity on all glycosidases, without any significant change in enzyme specificity toward monosaccharide (glucose or galactose) or glycoside (C-6 position free or phosphorylated). However, the surface covalent modification of the enzymes showed very interesting results. The glycosidase Lp_0440 showed low glycoside specificity at 25 °C, showing the same activity against p-nitrophenyl-glucopyranoside (pNP-Glu) or p-nitrophenyl-6-phosphate glucopyranoside (pNP-6P-Glu). However, the conjugated cHA-Lp_0440 showed a clear increase in the specificity towards the pNP-Glu and no activity against pNP-6P-Glu. The other two glycosidases (Lp_2777 and Lp_3525) showed high specificity towards pNP-6P-glycosides, especially to the glucose derivative. The HA covalent modification of Lp_3525 (cHA-Lp_3525) generated an enzyme completely specific against the pNP-6P-Glu (phosphoglycosidase) maintaining more than 80% of the activity after chemical modification. When the temperature was increased, an alteration of selectivity was observed. Lp_0440 and cHA-Lp_0440 only showed activity against p-nitrophenyl-galactopyranoside (pNP-Gal) at 40 °C, higher than at 25 °C in the case of the conjugated enzyme.

Site-selective modification of tryptophan and protein tryptophan residues through PdNP bionanohybrid-catalysed C–H activation in aqueous media

PdNP bionanohybrid catalyzed selective C–H bond arylation of tryptophan residues in proteins in aqueous media at room temperature.

Semisynthetic Enzymes by Protein-Peptide Site-Directed Covalent Conjugation: Methods and Applications

This chapter describes the rational design and synthesis of semisynthetic lipases by site-directed incorporation of tailor-made peptides on the lipase-lid site to improve its activity, specificity, and enantioselectivity in specific biotransformations. Cysteine was genetically introduced at a particular point of the oligopeptide lid of the enzyme, and cysteine-containing peptides, complementary to the amino acid sequence on the lid site of Geobacillus thermocatenulatus lipase (BTL), were covalently attached on the lid of two different cysteine-BTL variants based on a fast thiol-disulfide exchange ligation followed by desulfurization. The BTL variants were initially immobilized on solid support to introduce the advantages of solid-state chemistry, such as quantitative transformations, easy purification, and recyclability. In the two different immobilized variants BTL-A193C and BTL-L230C, the cysteine was then activated with 2-dipyridyldisulfide to help the disulfide exchange with the peptide, generating the semisynthetic enzyme in high yield. Excellent results of improvement of activity and selectivity were obtained. For example, the peptide-BTL conjugate (at position 193) was 40-fold more active than the corresponding unmodified enzyme for the hydrolysis of per-acetylated thymidine at pH 5, or fourfold in the desymmetrization of dimethyl-3-phenylglutarate at pH 7. The new enzyme also exhibited excellent enantioselectivity in the desymmetrization reaction with enantiomeric excess (ee) of >99% when compared to that of the unmodified enzyme (ee=78%).

Regioselective Palmitoylation of 9-(2,3-Dihydroxy- propyl)adenine Catalyzed by a Glycopolymer-enzyme Conjugate

The enzymatic regioselective monopalmitoylation of racemic 9-(2,3-dihydroxypropyl)- adenine (DHPA), an approved antiviral agent, has been performed by an immobilized form of Candida antarctica B lipase (CAL-B) using a 4:1 DMF/hexane mixture as the reaction medium. To improve the chemical yield of the desired monopalmitoylation reaction, solid-phase chemical modifications of the lipase were evaluated. The reaction yield was successfully increased obtaining 100% product after a second treatment of the product solution with fresh immobilised chemically glycosylated-CAL-B.

New emerging bio-catalysts design in biotransformations

The development of new and successful biotransformation processes of key interest in medicinal and pharmaceutical chemistry involves creating new biocatalysts with improved or even new activities and selectivities. This review emphasizes the new emerging developed strategies to achieve this goal, site-selective chemical modification of enzymes using tailor-made peptides, specific insertion of metals or organometallic complexes into proteins producing bio-catalysts with multiple activities and computational design for creating evolved artificial enzymes with non-natural synthetic catalytic activities.

Click reactions in protein chemistry: from the preparation of semisynthetic enzymes to new click enzymes

Click-chemistry is an approach based on cycloaddition reactions which has been successfully used as a chemical approach for complex organic molecules and which has recently starred in a boom in the world of protein chemistry. The advantage of the use of this technique in protein chemistry is based on a very high and efficient chemoselectivity, which usually requires simple or no purification and is extremely rate-accelerated in aqueous media. The perspective discusses some of the most recent advances in the application of this reaction in selective enzyme surface modification for the creation of new semisynthetic enzymes (fluorescence labeled enzymes, peptide-enzyme conjugates, glycosylated enzymes), and interestingly, the recent design and creation of "click" enzymes.