Enzymes horse liver alcohol dehydrogenase

Figure 8.27 Reduction of aldehyde in SCCO2 by an isolated enzyme, horse liver alcohol dehydrogenase (HLADH) [20c] (a) Reaction scheme (b) fluorinated coenzyme soluble in CO2 and (c) effect of coenzyme on the reaction.

JB Jones. An illustrative example of a synthetically useful enzyme horse liver alcohol dehydrogenase. In R Porter, S Clark eds. Enzymes in Organic Synthesis. London Pitman Publishing, 1985, pp 3-21. 

Previously, Beckman and co-workers had prepared nicotinamide adenine dinucleotide (NAD) with a fluorophilic ponytail (FNAD). This molecule was able to act as an affinity surfactant and extract the enzyme horse liver alcohol dehydrogenase (HLADH) from an aqueous medium into methoxynona-fluorobutane (HFE) (Figure 7.24). Interestingly, the addition of potential... 

Panza et al. synthesized a C02-philic amphiphile from the coenzyme nicatinamide adenine dinucleotide (MW 664) and a covalently attached perfluoropolyether (MW 2500) (Figure 7B) (73). The fluorofunctional coenzyme (FNAD) was soluble up to 5 mM in CO2 at room temperature and 1400 psi. The C02-soluble FNAD was able to participate in a cyclic oxidation/reduction reaction catalyzed by the enzyme horse liver alcohol dehydrogenase (HLADH) in CO2 at room temperature and 2600 psi. 

In a second synthesis of labeled phenylalanine Battersby et al. (305, 306) used the pro-R specific enzyme horse liver alcohol dehydrogenase to reduce [ HJbenzaldehyde 306, Ha = H. The (lS)-[l- H,]benzyl alcohol 307 obtained was converted via tosylation and reaction with malonate anion to the acid 308 (Scheme 81), which, on bromination and ammonolysis, gave (2RS, 3R)-[3- Hi]phenylalanine 297, He = H. Ife and Haslam (309) used the more direct replacement of the tosylates of the alcohol 307 with acetamidomalonic ester in a similar synthesis of (3R)- and (3S)-[3- Hi]pheny-lalanines. Fermenting yeast replaced liver alcohol dehydrogenase in a further synthesis (310). 

Fig. 13. Phosphorescence emission of the enzyme horse liver alcohol dehydrogenase at 1.3 K in 50 % ethylene glycol-water showing the optically-resolved origins of the two tryptophan sites of the enzyme. Excitation is at 295 nm. (From Zuclich et al. 1 )...

ADH Horse liver alcohol dehydrogenase, an enzyme dimer of identical 374 amino acid polypeptide chains. The amino acid composition of ADH is reasonably representative of die norm for water-solnble proteins. 

In the case of horse liver alcohol dehydrogenase, a homodimeric enzyme, Subramanian et al.(202) used the relative phosphorescence of tyrosine and tryptophan to examine the effects of various ternary complexes known to selectively quench the fluorescence of the tryptophans of each subunit. One proposed quenching mechanism is the formation of a ground-state tyrosinate in a ternary complex at neutral pH.(201) This tyrosinate, by being a resonance... 

In the following year, Cleland and his coworkers reported further and more emphatic examples of the phenomenon of exaltation of the a-secondary isotope effects in enzymic hydride-transfer reactions. The cases shown in Table 1 for their studies of yeast alcohol dehydrogenase and horse-liver alcohol dehydrogenase would have been expected on traditional grounds to show kinetic isotope effects between 1.00 and 1.13 but in fact values of 1.38 and 1.50 were found. Even more impressively, the oxidation of formate by NAD was expected to exhibit an isotope effect between 1.00 and 1/1.13 = 0.89 - an inverse isotope effect because NAD" was being converted to NADH. The observed value was 1.22, normal rather than inverse. Again the model of coupled motion, with a citation to Kurz and Frieden, was invoked to interpret the findings. 

Fig. 6 Illustration from Chin and Klinman. Increased catalytic activity of horse-liver alcohol dehydrogenase in the oxidation of benzyl alcohol to benzaldehyde by NAD, measured by cat/ M (ordinate), correlates with the Swain-Schaad exponent for the -secondary isotope effect (abscissa), for which values above about four are indicators of tunneling. This is a direct test of the hypothesis that tunneling in the action of this enzyme contributes to catalysis. As the rate increases by over two orders of magnitude and then levels off, the anomalous Swain-Schaad exponents also increase and then level off. Reproduced from Ref. 28 with the permission of the American Chemical Society.

However, a pure enzyme, like horse liver alcohol dehydrogenase (HLADH), shows not only high stereoselectivity but regioselectivity as well, affording, for example, 89% yield of monoalcohol 5 from dione 4 with ee higher than 99% [14]. 

All the enzymes used in the work described above are quite stable at room temperature and can be used in a free form. They can also be used in an immobilized form to improve the stability and to facilitate the recovery. Many immobilization techniques are available today (25). The recent procedure developed by Whitesides et al using water-insoluble, cross-linked poly(aerylamide-acryloxysuccinimide) appears to be very useful and applicable to many enzymes (37). We have found that the non-crosslinked polymer can be used directly for immobilization in the absence of the diamine cross-linking reagent. Reaction of an enzyme with the reactive polymer produces an immobilized enzyme which is soluble in aqueous solutions but insoluble in organic solvents. Many enzymes have been immobilized by this way and the stability of each enzyme is enhanced by a factor of greater than 100. Horse liver alcohol dehydrogenase and FDP aldolase, for example, have been successfully immobilized and showed a marked increase in stability. 

The enzyme chemistry of cyclopropylmethanols has been studied both as inhibitors and mechanistic probes [4, 47]. Thus, a series of alkylcyclopropyl-methanol derivatives have been proved as being inhibitors of horse liver alcohol dehydrogenase. There are two sites in the cyclopropylmethanol inhibitors able of reacting with nucleophiles ... 

Another zinc-utilizing enzyme is carbonate/dehydratase C (Kannan et al., 1972). Here, the zinc is firmly bound by three histidyl side chains and a water molecule or a hydroxyl ion (Fig. 27). The coordination is that of a distorted tetrahedron. Metals such as Cu(II), Co(Il), and Mn(ll) bind at the same site as zinc. Hg(II) also binds near, but not precisely at, this site (Kannan et al., 1972). Horse liver alcohol dehydrogenase (Schneider et al., 1983) contains two zinc sites, one catalytic and one noncatalytic. X-Ray studies showed that the catalytic Zn(II), bound tetrahedrally to two cysteines, one histidine, and water (or hydroxyl), can be replaced by Co(II) and that the tetrahedral geometry is maintained. This is also true with Ni(Il). Insulin also binds zinc (Adams etai, 1969 Bordas etal., 1983) and forms rhombohedral 2Zn insulin crystals. The coordination of the zinc consists of three symmetry-related histidines (from BIO) and three symmetry-related water molecules. These give an octahedral complex... 

AOT/isooctane/ buffer Horse liver alcohol dehydrogenase Microemulsion system that is temperature sensitive to phase separate was used for recovery of proteins and enzymes [283]... 

Horse liver alcohol dehydrogenase (HLADH (E.C. 1.1.1.1), commercially available) is a well-documented enzyme capable of catalyzing the enantioselective oxidation of acyclic and cyclic meso-configurated dimethanol derivatives to chiral lactols and further to the corresponding chiral lactones with high enantioselectivity and in high yield (Table 11) 162 ,69. Incases where the two enantiomeric lactols are formed, a kinetic enantiomer separation can occur in the second oxidation step166. 

Horse liver alcohol dehydrogenase is able to oxidise primary alcohols—except methanol—and to reduce a large number of aldehydes. Aqueous solution or organic solvents can be used [62]. As there are no new developments concerning this enzyme, the reader is referred to the review of Schreier [1]. 

The reduction of 3- and 4-thiepanones (41 and 42) was reported using either hydride (LAH) (67AG(E)872, 70JOC584) or horse liver alcohol dehydrogenase enzymes which gave the 3-hydroxy- (136) and 4-hydroxy- (43) thiepane in optically active form (81CJC1574. ... 

The dimensions of cavities in enzymes differ considerably, depending on their physiological function. In many cases the clefts are occupied by clusters of organized water molecules. Such clusters can be seen in certain X-ray structures of enzymes (e.g., the structure of carboxypeptidase A determined by Lipscomb). If the clefts are deep, as in horse liver alcohol dehydrogenase, a channel for removal of water is present (Branden). 

A crystal structure of a ternary complex of horse liver alcohol dehydrogenase with NADH and the inhibitor, dimethyl sulfoxide, first at 4.5 A resolution1365 and a further refinement to 2.9 A resolution,1366 has been published by Eklund et al. The gross structure of the ternary complex is similar to that of the free enzyme structure. Each subunit is divided into a coenzyme-binding domain and a catalytic domain. The subunits are joined together near the... 

The use of ester-cleaving enzymes is probably going to be one of the most useful biological-chemical methods in the synthetic laboratory. No example of this type of reaction has hitherto been published in the Organic Syntheses series of procedures. So far, the only biological-chemical Organic Synfheses-procedures are two yeast reductions,4 5 one oxidation with horse-liver-alcohol-dehydrogenase,6 and a disaccharide synthesis catalyzed by emulsin.7 The procedure described here is... 

Enzymes as different as yeast alcohol oxidase, mushroom polyphenol oxidase, and horse-liver alcohol dehydrogenase demonstrated vastly increased enzymatic activity in several different solvents upon an increase in the water content, which always remained below the solubility limit (Zaks, 1988b). While much less water was required for maximal activity in hydrophobic than in hydrophilic solvents, relative saturation seems to be most relevant to determining the level of catalytic activity. Correspondingly, miscibility of a solvent with water is not a decisive criterion upon transition from a monophasic to a biphasic solvent system, no significant change in activity level was observed (Narayan, 1993). Therefore, the level of water essential for activity depends more on the solvent than on the enzyme. 

Other microorganisms and isolated enzymes have been also used for the oxidation of alcohols (Figure 26).27 Horse liver alcohol dehydrogenase was used for the oxidation of meso diols (Figure 26 (d, e)).27e,f When one of the hydroxyl groups was oxidized, cyclization proceeded spontaneously, followed by the enzyme-catalyzed oxidation, giving chiral lactones. 

KP Lok, TJ Jakovac, JB Jones. Enzymes in organic synthesis. 34. Preparation of enantiomerically pure exo- and endo-bridged bicyclic [2.2.1] chiral lactones via stereospecific horse liver alcohol dehydrogenase catalyzed oxidations of meso di-ols. J Am Chem Soc 107 2521-2526, 1985. 

Another gap of almost 10 years occurred before work in the area of CLCs picked up again. In 1985, a group at the Louis Pasteur University in Strasbourg, France, prepared cross-linked crystals of horse liver alcohol dehydrogenase [4], The activity of the enzyme in CLC form was maintained and the coenzyme was found to be firmly bound to the crystals. The cross-linked crystals could be used as redox catalysts with no addition of coenzyme. The authors also reported the increased stability of CLCs toward organic solvents. 

Horse liver alcohol dehydrogenase is a well-documented enzyme capable of operating with high stereoselectivity on a broad structural range of alcohol and carbonyl substrates. The present reaction proceeds via the pathway shown below, where NAD and NADH represent the oxidized and reduced forms, respectively, of the nicotinamide adenine dinucleotide coenzyme. 

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