Lactate dehydrogenase cross-linking

Enzymes in the cross-linked crystal form are essentially impervious to degradation by exogenous proteases and from autolysis, in the case of CLCs of proteases themselves [5], This stability makes the enzyme-catalyzed preparation of peptides and peptide mimics truly practical [6], Examples will be discussed in more detail in Sec. IV. Further, one could conceive of using multiple enzymes in one-pot reaction systems mimicking natural biosynthetic cascades. Indeed, the application of this concept has been reported for a mixture of lipoamide dehydrogenase and lactate dehydrogenase [19],... 

Reduction of achiral precursors is often used to produce chiral products. The advantage of this approach is that the theoretical yield of product is 100% compared to the 50% theoretical maximum for the resolution of racemates. Cross-linked crystals of lactate dehydrogenase have been used to prepare L-lactic acid from pyruvic acid in an electrolytic cell. The LDH CLCs maintained constant... 

Figure 20. (A) The assembly of an integrated lactate dehydrogenase monolayer electrode by the cross-linking of an affinity complex formed between the enzyme and a PQQ-NAD monolayer-modified Au electrode. (B) Cyclic voltammograms of the integrated cross-linked PQQ-NAD / lactate dehydrogenase electrode (roughness factor ca. 15) (a) in the absence of lactate (b) with lactate, 20 mM. Recorded in 0.1 M Tris buffer, pH 8.0, in the presence of 10 mM CaCb, under Ar potential scan rate, 2 mV s . Inset amperometric responses of the integrated electrode at different concentrations of lactate upon application of potential 0.1 V vs. SCE.

Figure 8. Methyl viologen-mediated electroenzymatic reduction of pyruvate to o-lactate using lipoamide dehydrogenase (LiDH) and cross-linked enzyme crystals of o-lactate dehydrogenase [49],...

Active immobilized enzymes were obtained when a cellulose isothiocyanate reacted with glucoamlyase and when cellulose cross-linked with formaldehyde and treated with 2-chlorotriethylamine reacted with D-glucose isomerase. Alcohol dehydrogenase and lactate dehydrogenase have been immobilized, without loss of the enzymic activities, on s-triazinylated DEAE-cellulose. 

Lactate is a small biological molecule that functions as metabolite in the mitochondria and a precursor to pyruvate in the citric acid cycle [87]. In 1997, Bardea et al. developed a lactate BFC using NAD -dependent lactate dehydrogenase (LDH) [88]. They introduced a new method for enzyme immobilization that enabled better oxidation of the substrate and allowed the enzyme to have eleetrieal eontact with the electrode. Covalently linked PQQ and native NAD" form a monolayer on gold electrodes to induce affinity interactions with cross-linked NAD -dependent LDH. In 2001, Katz et al. further improved on the concept of this anode, coupling it with a cytochrome c oxidase cathode to produce a self-powered biosensor that is active only in the presence of the anode s substrate, lactate [89]. With this addition, the cell is completely dependent on substrate for voltage and current output, which is ideal for BFCs. 

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