Functionalised bilayer vesicle as a catalyst for transamination: artificial transaminase

Abstract

The non-enzymic transamination reaction of a-amino acids with a-keto acids was investigated in aqueous media at 30.0 "C. The functionalised single-walled co-vesicle composed of a synthetic peptide lipid, hexanoyl] -L-histidinamide bromide, and a hydrophobic pyridoxal derivative, 1 -(NN-di hexadecylcarbamoylmethyl) -2-methyl -3hydroxy-4-formyl-5hydroxymet hy I pyridi n iu m chloride, effectively catalysed am i no-group transfer from L-p henylalanine to pyruvic acid in the presence of copper(ii) ions, showing turnover behaviour. The catalytic activity of the vesicular system was much higher than those of 1,2-dimethyl-3-hydroxy-4-formyl-5-hydroxymethylpyridinium chloride and pyridoxal examined in aqueous media containing copper( ii) ions. The ratedetermining step involved in the catalytic cycle performed with the vesicular catalyst is primarily assigned t o the product-releasing process, the hydrolysis of the copper(i1) chelate of the aldimine Schiff's base to afford alanine.Vitamin B,-dependent transaminases catalyse the amino-group transfer from a-amino acids (AA) to a-keto acids (KA') and take part in amino-acid metabolism.' It is well known that the catalytic cycle is completed by the sequential reactions in the enzymic system shown in the Scheme: (i) formation of the aldimine Schiffs base (ASB) of AA with the coenzyme, pyridoxal 5'-phosphate (PLP), which is tightly bound to the apoprotein (step A); (ii) isomerization of ASB to the ketimine Schiffs base (KSB) (step B); (iii) hydrolysis of KSB to give an aketo acid (KA) and pyridoxamine 5'-phosphate (PMP) (step C); (iv) reversal of this sequence of reactions, starting with P M P and another a-keto acid (KA'), to afford PLP and the corresponding a-amino acid (AA') uiu formation of the ketimine and aldimine Schiff s bases (KSB' and ASB', respectively) (steps D -E -F). Although the half-transamination reactions (A -B C; D -E -F) proceed in non-enzymic

A nanosensory device fabricated on a liposome for detection of chemical signals

“…The pyridoxal derivatives 1-hexadecyl-2-methyl-3-hydroxy-4-formyl-5-hydroxymethylpyridinium chloride (R 1 ) and 1,2-dimethyl-3-hydroxy-4-formyl-5-hydroxymethylpyridinium chloride (R 2 ) were synthesized through the method similar to that previously reported (Kondo et al, 1985;Murakami et al, 1985). The following compounds were commercially available as guaranteed reagents and used without further purification: LDH from pig heart (Boehringer Mannheim GmbH, Mannheim, Germany); b-nicotinamide adenine dinucleotide disodium salt (NADH) (Sigma-Aldrich Co., St. Louis, MO); sodium pyruvate (Wako Pure Chemical Industries Ltd., Osaka, Japan); copper(II) perchlorate hexahydrate (Kanto Chemical Co., Inc., Tokyo, Japan); tryptamine (S 1 ) (SigmaAldrich Co.); taurine (S 2 ), serotonin (S 3 ), histamine (S 4 ), and dopamine (S 5 ) (Wako Pure Chemical Industries Ltd.), and alkyl amines (Tokyo Kasei Kogyo Co. Ltd., Tokyo, Japan).…”

Emergent properties arising from the assembly of amphiphiles. Artificial vesicle membranes as reaction promoters and regulators

“…6), the complexation of inorganic ions as catalysts (or co-catalysts) in vesicle membranes is also possible, as for example demonstrated by Murakami and coworkers. 133,135,146,148,171 In this pioneering and very detailed work, the transamination of the hydrophobic amino acid L-Phe with pyruvate, a hydrophilic a-keto acid, was investigated and found to be catalyzed at pH = 5.1 (T = 30 1C) by vesicle membranes composed of a mixture of two cationic amphiphiles, one bearing a pyridoxamine group (abbreviated as PL + 2C 16 ), the other bearing a histidyl residue (N + C 5 His2C 16 ), and copper(II) ions as the inorganic ions. The reaction products obtained from L-Phe and pyruvate are Ala (as racemate) and phenylpyruvate, see Fig.…”

“…This is why this functionalized vesicle system can be considered as ''artificial aminotransferase'' mimic. 133,135,171,172 Under optimal reaction conditions, vesicles formed from N + C 5 Lys2C 16 and PL + 2C 16 catalyzed with an enatiomeric excess (ee) of 90-92% the transformation of L-Phe and pyruvate into D-Ala and phenylpyruvate at pH = 7.0 and T = 30 1C. 148 In much less sophisticated vesicle systems, the metalcatalyzed hydrolysis of activated esters occurring on the surface of the vesicles was investigated.…”

Smart Vesicles: Synthesis, Characterization and Applications

“…[245][246][247][248][249][250][251][252][253] Another possible way of catalytic application of vesicles is by making hard metallic vesicles based on soft vesicles. illustrate the promise of approaches in which a catalyst such as a metal ion is used as the counterion (Fig.…”