Phenylalanine aminotransferase

The activity was generally higher in cells grown in a cultivation medium containing D- or L-phenylalanine, mis confirmed the inducible nature of the phenylalanine aminotransferase. 

Figure 1. Schematic outline of various products and associated enzymes from the shikimate and phenolic pathways in plants (and some microorganisms). Enzymes (1) 3-deoxy-2-oxo-D-arabino-heptulosate-7-phosphate synthase (2) 5-dehydroquinate synthase (3) shikimate dehydrogenase (4) shikimate kinase (5) 5-enol-pyruvylshikimate-3-phosphate synthase (6) chorismate synthase (7) chorismate mutase (8) prephenate dehydrogenase (9) tyrosine aminotransferase (10) prephenate dehydratase (11) phenylalanine aminotransferase (12) anthranilate synthase (13) tryptophan synthase (14) phenylalanine ammonia-lyase (15) tyrosine ammonia-lyase and (16) polyphenol oxidase. (From ACS Symposium Series No. 181, 1982) (62).

PHENYLALANINE AMINOTRANSFERASE PHENYLALANINE AMMONIA-LYASE PHENYLALANINE DECARBOXYLASE PHENYLALANINE DEHYDROGENASE PHENYLALANINE MONOOXYGENASE PHENYLALANINE RACEMASE PHENYLALANINE AMINOTRANSFERASE AROMATIC AMINO ACID AMINOTRANSFERASE... 

PHENYLALANINE AMMONIA-LYASE DEHYDROALANINE BOROHYDRIDE REDUCTION PHENYLALANINE DECARBOXYLASE PHENYLALANINE DEHYDROGENASE Phenylalanine(histidine) aminotransferase, PHENYLALANINE AMINOTRANSFERASE PHENYLALANINE HYDROXYLASE (Phenylalanine Monooxygenase)... 

Other pyruvate-containing enzymes include aspartate -decarboxylase from Escherichia coli, the enzyme that catalyzes the formation of -alanine for the synthesis of pantothenic acid (Section 12.2.4) proline reductase from Clostridium sticklandiv, phosphatidylserine decarboxylase from E. coli and phenylalanine aminotransferase from Pseudomonas fluorescens. Phospho-pantetheinoyl cysteine decarboxylase, involved in the synthesis of coenzyme A (Section 12.2.1), and S-adenosylmethionine decarboxylase seem to be the only mammalian pyruvoyl enzymes (Snell, 1990). 

Chorismate mutase 2 prephenate aminotransferase 3 prephenate dehydratase 4 prephenate dehydrogenase 5 arogenate dehydrogenase 6 phenylalanine aminotransferase 7 tyrosine aminotransferase 8 tyrosine 3-monooxygenase 9 phenylalanine 4-monooxygenase (C 2.6.5)... 

L-Phenylalanine aminotransferases (classified as tyrosine aminotransferase, E.C. 2.6.1.5 which also acts on phenylalanine) are enzymes useful in L-phenylalanine synthesis, as mentioned above, and have been studied in various thermophilic bacteria by Schutten et al. [185]. These workers looked at several Bacillus isolates... 

Practical conversion from ACA to L-phenylalanine was best achieved when acylase and aminotransferase activities were equal. This could be achieved by using 10 gram B. sphaericus and 25 gram P. denitrificam per litre medium. 

The probable metabohc defect in type I tyrosine-mia (tyrosinosis) is at himarylacetoacetate hydrolase (reaction 4, Figure 30-12). Therapy employs a diet low in tyrosine and phenylalanine. Untreated acute and chronic tyrosinosis leads to death from liver failure. Alternate metabolites of tyrosine are also excreted in type II tyrosinemia (Richner-Hanhart syndrome), a defect in tyrosine aminotransferase (reaction 1, Figure 30-12), and in neonatal tyrosinemia, due to lowered y>-hydroxyphenylpyruvate hydroxylase activity (reaction 2, Figure 30-12). Therapy employs a diet low in protein. 

This enzyme [EC 2.6.1.58], also referred to as phenylala-nine(histidine) aminotransferase, catalyzes the reversible reaction of L-phenylalanine with pyruvate to produce phenylpyruvate and L-alanine. This enzyme will also use L-histidine and L-tyrosine as substrates. In the reverse reaction, L-methionine, L-serine, and L-gluta-... 

This pyridoxal-phosphate-dependent enzyme [EC 2.6.1.5], also known as tyrosine transaminase, catalyzes the reaction of L-tyrosine with a-ketoglutarate (or, 2-oxoglutarate) to produce 4-hydroxyphenylpyruvate and L-glutamate. L-Phenylalanine can act as the substrate instead of tyrosine. In some systems, the mitochondrial enzyme may be identical with aspartate aminotransferase. 

AROMATIC AMINO ACID-GLYOXYLATE AMINOTRANSFERASE Aromatic amino acid hydroxylases, PHENYLALANINE HYDROXYLASE TYROSINE HYDROXYLASE TRYPTOPHAN HYDROXYLASE ARRHENIUS CONSTANT... 

KYNURENINE AMINOTRANSFERASE LEUCINE AMINOTRANSFERASE LYSINE 2,3-AMINOMUTASE LYSINE 6-AMINOTRANSFERASE LYSINE DECARBOXYLASE METHIONINE y-LYASE ORNITHINE AMINOTRANSFERASE PHENYLALANINE DECARBOXYLASE PHOSPHATIDYLSERINE DECARBOXYLASE... 

Figure 3-5. Biosynthesis of salicylic acid. The enzymes involved in this pathway are (a) chorismate mutase (E.C. 5.4.99.5), (b) prephenate aminotransferase (E.C. 2.6.1.78 and E.C. 2.6.1.79), (c) arogenate dehydratase (E.C. 4.2.1.91), (d) phenylalanine ammonia lyase (E.C. 4.3.1.5), (e) presumed P-oxidation by a yet to be identified enzyme, (f) benzoic acid 2-hydroxylase, (g) isochorismate synthase (E. C. 5.4.4.2), and (h) a putative plant pyruvate lyase.

Free amino acids are further catabolized into several volatile flavor compounds. However, the pathways involved are not fully known. A detailed summary of the various studies on the role of the catabolism of amino acids in cheese flavor development was published by Curtin and McSweeney (2004). Two major pathways have been suggested (1) aminotransferase or lyase activity and (2) deamination or decarboxylation. Aminotransferase activity results in the formation of a-ketoacids and glutamic acid. The a-ketoacids are further degraded to flavor compounds such as hydroxy acids, aldehydes, and carboxylic acids. a-Ketoacids from methionine, branched-chain amino acids (leucine, isoleucine, and valine), or aromatic amino acids (phenylalanine, tyrosine, and tryptophan) serve as the precursors to volatile flavor compounds (Yvon and Rijnen, 2001). Volatile sulfur compounds are primarily formed from methionine. Methanethiol, which at low concentrations, contributes to the characteristic flavor of Cheddar cheese, is formed from the catabolism of methionine (Curtin and McSweeney, 2004 Weimer et al., 1999). Furthermore, bacterial lyases also metabolize methionine to a-ketobutyrate, methanethiol, and ammonia (Tanaka et al., 1985). On catabolism by aminotransferase, aromatic amino acids yield volatile flavor compounds such as benzalde-hyde, phenylacetate, phenylethanol, phenyllactate, etc. Deamination reactions also result in a-ketoacids and ammonia, which add to the flavor of... 

Previously, AAT had been transformed into an L-tyrosine aminotransferase (TAT) by site-specific mutation of up to six amino acid residues lining the active site of wild-type AAT. The hextuple AAT-mutant achieved kinetic data towards the transamination of aromatic substrates such as i-phenylalanine within an order of magnitude of wild-type TAT (Onuffer, 1995). 

Chloramphenicol.—A synthetase which converts chorismic acid into p-amino-phenylalanine (an intermediate in chloramphenicol biosynthesis) has been partly characterized it requires an aminotransferase and pyridoxal phosphate for activity.58... 

Phenylalanine(histidine) aminotransferase 3 -SULFIN OALANINE-AMINOTRANSFERASE-RXN 0.2415238... 

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