Dehydrogenase alanine

Enantiopure (5)-fluoroalanine has been prepared by an enzymatic path starting from 3-fluoropyruvate in the presence of alanine dehydrogenase, and also by chemical synthesis from (5)-p-tolyl methyl sulfoxide (Figure 5.1) or from the L-serine. The analogue labeled with F has been prepared for use in positron emission tomography (PET) used in cancer diagnosis. ... 

An example of coenzyme regeneration with isolated enzymes is L-alanine production from pyruvate with an NADH-dependent alanine dehydrogenase (AlaDH) ... 

T. Ohshima, C. Wandrey, M. Sugiura, and K. Soda, Screening of thermostable leucine and alanine dehydrogenases in thermophilic Bacillus strains, Biotechnol. Lett. 

Answer Lactate and alanine are converted to pyruvate by their respective dehydrogenases, lactate dehydrogenase and alanine dehydrogenase, producing pyruvate and NADH + H+ and, in the case of alanine, NH. Complete oxidation of 1 mol of pyruvate to C02 and H20 produces 12.5 mol of ATP via the citric acid cycle and oxidative phosphorylation (see Table 16-1). In addition, the NADH from each dehydrogenase reaction produces 2.5 mol of ATP per mole of NADH reoxidized. Thus oxidation produces 15 mol of ATP per mole of lactate. Urea formation uses the equivalent of 4 mol of ATP per mole of urea formed (Fig. 18-10), or 2 mol of ATP per mol of NH4. Subtracting this value from the energy yield of alanine results in 13 mol of ATP per mole of alanine oxidized. 

Several sensors for L-alanine are obtained by immobilizing L-alanine dehydrogenase over an ammonia gas-sensing electrode (288) or over an O2 sensor (280). The enzyme catalyzes the specific deamination of alanine in the presence of the coenzyme NAD ... 

Co-immobilizing a second enzyme, NADH oxidase (280) or lactate dehydrogenase (288), permits the regeneration of NAD+. Measurements may be completed in Tris-HCl or carbonate buffers, but borate and glycine buffers inhibit L-alanine dehydrogenase (289). Highly selective L-histidine electrodes are available (290, 291) to determine histidine in urine (291). 

EC 1.4.1.1 Alanine dehydrogenase pyruvate+nadred+ammonia=alanine+nadox+h2o... 

Gilis et al. [117] developed biosensors for the determination of L-alanine and its precursor pyruvate. They adapted the principle of a photometric assay, which was based on alanine dehydrogenase (Eq. (11.6))... 

The application of the same principle to the formation of o-alanine is possible but lacks applicability due to its slowness. In this case, in the presence of ammonia, pyruvate is in equilibrium with its imine. This is reduced at the cathode under formation of racemic alanine. The L-alanine of the racemic mixture is reoxidized by L-alanine dehydrogenase under anodic regeneration of the necessary cofactor NAD to give pyruvate and ammonia, while the o-alanine is not accepted by the enzyme and accumulates in the reaction mixture. The drawback of this reaction is the kinetic control by imine formation, which is very slow, so that a complete inversion of a lOmAf solution of L-alanine would require 140 h [105]. 

The synthesis of alanine from glucose will be discussed here. In the database of 250 reactions used by Mavrovouniotis et al. (1992), six reactions involve glucose, and four involve alanine alanine dehydrogenase, methylserine hydroxymethyltransferase, alanine aminotransferase, and jS-alanine aminotransferase). 

Y2. Yoshida, A., Enzyme purification by selective elution with substrate analog from ion-exchange columns Application to glucose 6-phosphate dehydrogenase, pseudocholinesterase, lactate dehydrogenase, and alanine dehydrogenase. Anal. Biochem. 37, 357-367 (1970). 

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