Lyase catalysis

Kramer, P R., and Miziorko, H. M- (19B3J. 3-Hydro)ty-3-methylglutary CoA lyase Catalysis of acetyl coenzyme Aenolization. Biw/rcrrifstry 22, 2353-2357-... 

Lou W-Y, Xu R, Zong M-H (2005) Hydroxynitrile lyase catalysis in ionic liquid-containing systems. Biotechnol Lett 27 1387-1390... 

Figure 7-5. Two-dimensional representation of Koshland s induced fit model of the active site of a lyase. Binding of the substrate A—B induces conformational changes In the enzyme that aligns catalytic residues which participate in catalysis and strains the bond between A and B, facilitating its cleavage.

Ethanolamine ammonia lyase has a molecular weight of 520,000 and consists of 8 or 10 subunits. Two 5 -deoxyadenosylcobalamin molecular bind per enzyme molecule, and recent kinetic studies by Babior show that these two molecules carry out catalysis independently. Evidence is available that this enzyme functions by a radical mechanism since both spin labeling and Co(II) esr experiments indicate that Co(II) is an intermediate during H-transfer. Also, 5 -deoxyadenosine has been detected as a product of oxygenation of the enzyme-substrate complex (99—101). 

Spin labeled 5 -deoxyadenosylcobinamide has been used as a cofactor for ethanolamine-ammonia-lyase and the ESR spectrum followed during catalysis (123). This spin labeled coenzyme is biologically active in this enzyme. Enzyme kinetics showed this derivative to have the same Vmax as the cofactor 5 -deoxyadenosylcobinamide, but it has a higher Km value of 5.1 X 10-6 M compared to 4.6 X 10-6 for 5 -deoxyadenosylcobinamide (123). When the spin labeled coenzyme was incubated with apoenzyme to give the enzyme-coenzyme complex, the nitroxide ESR spectrum resembled that of free spin label but the lines are broadened significantly. 

The application of magnetic resonance techniques to biological systems is a relatively new approach for the study of macromolecules. In this review we have presented the different approaches which have been made to study Bi2-enzymes. Clearly some progress has been made particularly from the application of ESR to a study of the enzymes ethanolamine ammonia-lyase and ribonucleotide reductase. Although 13C NMR is well in its developmental stages it is obvious that this technique will prove to be very useful for the examination of coenzyme-enzyme interactions. Studies of how corrinoids bind in enzymes and how sulfhydryl containing proteins are involved in enzyme catalysis comprise two major problems which must be overcome before realistic mechanisms can be presented for this group of enzymes. 

Effenberger, F., Forster, S. and Wajant, H. (2000) Hydroxynitrile lyases in stereoselective catalysis. Current... 

Hernandez, L., Luna, H., Rulz-Teran, F. and Vazquez, A. (2004) Screening for hydroxynitrile lyase activity in crude preparations of some edible plants. Journal of Molecular Catalysis B-Enzymatic, 30, 105-108. 

Von Langermann, J., Mell, A., Paetzold, E. et al. (2007) Hydroxynitrile lyase in organic solvent-free systems to over come thermodynamic limitations. Advanced Synthesis and Catalysis, 349, 1418-1424. 

Costes, D., Wehtje, E. and Adlercreutz, P. (2001) Cross-linked crystals of hydroxynitrile lyase as catalyst for the synthesis of optically active cyanohydrins. Journal of Molecular Catalysis B-Enzymatic, 11, 607-612. 

The realization of the widespread occurrence of amino acid radicals in enzyme catalysis is recent and has been documented in several reviews (52-61). Among the catalytically essential redox-active amino acids glycyl [e.g., anaerobic class III ribonucleotide reductase (62) and pyruvate formate lyase (63-65)], tryptophanyl [e.g., cytochrome peroxidase (66-68)], cysteinyl [class I and II ribonucleotide reductase (60)], tyrosyl [e.g., class I ribonucleotide reductase (69-71), photosystem II (72, 73), prostaglandin H synthase (74-78)], and modified tyrosyl [e.g., cytochrome c oxidase (79, 80), galactose oxidase (81), glyoxal oxidase (82)] are the most prevalent. The redox potentials of these protein residues are well within the realm of those achievable by biological oxidants. These redox enzymes have emerged as a distinct class of proteins of considerable interest and research activity. 

Calabrese JC, Jordan DB, Boodhoo A, Sariaslani S, Vannelli T (2004) Crystal structure of phenylalanine ammonia lyase multiple helix dipoles implicated in catalysis. Biochemistry 43(36) 11403-11416... 

In several recent applications of enzyme catalysis, the snbstrates on which the enzymes act are not the kind of snbstrates that are natnral to the enzyme. However, enzyme catalysed synthesis of hexoses in the laboratory depends solely on enzymes acting on natural or near natnral snbstrates. The relevant enzymes are the aldolases (EC 4.1.2 aldehyde-lyases) since they catalyse an aldol type of C-C bond forming aldol addition reaction. The aldolases most commonly join two C-3 units, called donor and acceptor, and two new stereocentra are formed with great stereoselectivity. 

Fig. 2.2.3.S Preferred substrates of Sf HNL. 4-Hydroxy-mandelonitrile and tyrosyl-arginine are the preferred substrates of the main hydroxynitrile lyase activity and the carboxypeptidase side-activity. Since both substrates resemble the aromatic ring of tyrosine, catalysis at the same active site can be assumed.

F. Effenberger, S. Forster, H. Wajant, Hydroxynitrile lyases in stereoselective catalysis. Curr. Opin. Biotechnol. 2000,... 

M. Hasslacher, C. Kratky, H. Griengl, H. Schwab, S. D. Kohlwein, Hydroxynitrile lyase from Hevea hrasiliensis, molecular characterization and mechanism of enzyme catalysis. Proteins 1997, 27, 438-449. 

In nature, the green notes are produced after the destruction of the plants tissue (leaves, fruits or vegetables). Destruction of the cell wall leads to a cascade of enzyme-catalysed reactions polyunsaturated fatty acids with the diene system described before are converted into hydroperoxides by LOX catalysis. The hydroperoxide lyase cleaves the hydroperoxides in the whole cascade, oxireduc-tases are involved too. The biotechnological large-scale production of natural green notes follows the natural pathway. 

In the catalysis of the lyase from C. perfringens, the participation of lysine residues forming intennediary Schiff bases between enzyme and substrate molecules, and of histidine residues, has been demonstrated with the aid of photooxidation, reagents for histidine modification, and borohydride reduction in the presence of substrate.408-418 Thus, according to Frazi and coworkers,414 the lyase belongs to the class I lyases (aldolases). The catalytic mechanism proposed is outlined in Scheme 3. Evidence has been educed for the existence of a similar mechanism of cleavage of sialic acid by the lyase enriched from pig kidney.411... 

In the last decades, cyanohydrins have become versatile chiral building blocks, not only for laboratory synthesis, but also for a range of pharmaceuticals and agrochemicals. Several methods for the enantioselective preparation of these compounds have been published [1, 2]. The most important synthetic approaches are catalysis by oxynitrilases, also termed hydroxynitrile lyases (HNLs), wording used in this chapter, [3] and by transition metal complexes [4], whereas the relevance of cyclic dipeptides as catalysts is decreasing [2]. 

The enzymes that utilise Fe-S clusters and S-adenosylmethionine to generate radicals essential for catalysis are now identified as a class or superfamily, the radical-SAM enzymes. Hoffman et al. have studied the pyruvate formate-lyase activating enzyme (PFL-AE) by cw EPR (X-band) and pulsed ENDOR (2H and 13C, Q-band) and used the S = signals of the Fe4S4 cluster and derivatives to construct a model for the interaction of adenosylmethionine with the cluster.86... 

The majority of useful lyase families utilize anionically functionalized substrates such as pyruvate or dihydroxyacetone phosphate which remain unaltered during catalysis. The charged group thereby introduced into the products (phosphate, carboxylate) not only constitutes a handle for binding of the substrates by the enzymes but also can facilitate the preparative isolation from... 

Enzymatic reactions forming new carbon-carbon bonds are a further important field of biotransformations in natural product synthesis. The construction of new, often complex carbon frameworks or their decomposition is performed by nature under catalysis of a set of enzymes. For organic chemists some of these enzymes, belonging to the enzyme class of lyases, such as aldolases, decarboxylases, hydro-xynitrile lyases (HNLs), or benzaldehyde lyases (BALs), have been proven to represent versatile amendments to their synthetic toolbox. 

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