Brain Phenylalanine Aminotransferase: *

George, Harvey; Turner, Robert A.; Gabay, Sabit

doi:10.1111/j.1471-4159.1967.tb09889.x

Cited by 27 publications

(14 citation statements)

References 19 publications

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“…The enzymatic assay used in this study is based on the absorbance detection of complexes of IPyA and borate. In contrast to previously described assay procedures and to reduce toxicity, the assay in the present study was performed without arsenate as there was no difference in sensitivity detectable compared with arsenate addition (Fig. c).…”

Section: Resultsmentioning

confidence: 97%

Characterization of tryptophan aminotransferase 1 of Malassezia furfur, the key enzyme in the production of indolic compounds by M. furfur

Preuss

Hort

Lang³

et al. 2013

Experimental Dermatology

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Malassezia yeasts are responsible for the widely distributed skin disease Pityriasis versicolor (PV), which is characterized by a hyper- or hypopigmentation of affected skin areas. For Malassezia furfur, it has been shown that pigment production relies on tryptophan metabolism. A tryptophan aminotransferase was found to catalyse the initial catalytic step in pigment formation in the model organism Ustilago maydis. Here, we describe the sequence determination, recombinant production and biochemical characterization of tryptophan aminotransferase MfTam1 from M. furfur. The enzyme catalyses the transamination from l-tryptophan to keto acids such as α-ketoglutarate with Km values for both substrates in the low millimolar range. Furthermore, MfTam1 presents a temperature optimum at 40°C and a pH optimum at 8.0. MfTam1 activity is highly dependent on pyridoxal phosphate (PLP), whereas compounds interfering with PLP, such as cycloserine (CS) and aminooxyacetate, inhibit the MfTam1 reaction. CS is known to reverse hyperpigmentation in PV. Thus, the results of the present study give a deeper insight into the role of MfTam1 in PV pathogenesis and as potential target for the development of novel PV therapeutics.

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Section: Resultsmentioning

confidence: 97%

Characterization of tryptophan aminotransferase 1 of Malassezia furfur, the key enzyme in the production of indolic compounds by M. furfur

Preuss

Hort

Lang³

et al. 2013

Experimental Dermatology

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“…The buffer was 5 mM potassium phosphate at pH 7.5, and the homogenizer was an Ultra-Turrax (IKA-Works Inc., Wilmington, NC) drive with UT-dispersing tool T25 (S25N 18G) at 13,500 rpm. The homogenized tissue was analyzed for PAT according to the method of George et al (1967). Homogenates were sonicated at 10 kHz for 4 min using a 1/8-in stator (Sonics Vibra Cell ultrasonic processor, Sonics & Materials Inc., Newtown, CT).…”

Section: Pat Assaymentioning

confidence: 99%

“…After incubation at 37°C for 1 h, the reaction was terminated with the addition of 0.2 mL of 20% (wt/vol) trichloroacetic acid. One-half milliliter of the supernatant was mixed with 2.5 mL of arsenate-borate reagent (Lin et al, 1958) as described by George et al (1967) and was allowed to react for a minimum of 30 min. Aliquots of the reaction mixtures (0.25 mL) were transferred to 96-well UV plates and the absorbance at 300 nm was measured using a plate reader (Bio-Tek Instruments Inc., Winooski, VT).…”

Section: Pat Assaymentioning

confidence: 99%

Phenylalanine-pyruvate aminotransferase activity in chicks subjected to phenylalanine imbalance or phenylalanine toxicity

Austic

2009

Poultry Science

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Two experiments were done to determine the influence of Phe imbalance and excess on Phe-pyruvate aminotransferase (PAT) activity in the chick. Five replicates of 3 chicks (experiment 1) or 2 chicks (experiment 2) of a commercial brown egg layer strain were fed a semipurified diet for 1 wk and then received experimental diets for 10 d. Three diets were used in experiment 1: the basal diet contained 0.46% Phe; the imbalance diet was similar to the basal diet except that it contained a 10% mixture of indispensable amino acids lacking Phe (IAA - Phe) to create a Phe imbalance; the imbalance corrected diet was similar to the imbalance diet except that it was supplemented with 1.12% Phe to correct the imbalance. A 3 x 2 factorial arrangement of treatments in experiment 2 provided 3 dietary levels (0.46, 1.58, and 2.46%) of Phe and either no supplement or 10% supplement of IAA - Phe. Nonfasted chicks were killed and livers were sampled in experiment 1, and livers, kidneys, brains, and pectoralis major muscles were sampled in experiment 2. In experiment 1, liver PAT activity per gram of liver was 80 and 55% higher (P < 0.01) in chicks fed the imbalance and imbalance corrected diets than in chicks fed the basal diet. In experiment 2, the livers and kidneys, but not brains and muscles, of chicks that received the 10% supplement of IAA - Phe had higher activities of PAT per gram of tissue per minute and per milligram of tissue protein extract per minute than chicks that did not receive IAA - Phe (P < 0.001). No effect of dietary Phe on PAT activity was detected (P > 0.05). Phenylalanine-pyruvate aminotransferase activity appears to be regulated in response to dietary content of indispensable amino acids but not by the dietary level of Phe.

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“…Enzymatic activity towards phenylalanine, tyrosine and tryptophan was determined using a modification of the assay described by George et al [26]. This is based on the arsenatecatalyzed formation of aromatic 2-oxoacid-end-borate complexes that show characteristic absorption at 330, 310 and 300 nm for indolepyruvate, p-hydroxyphenylpyruvate and phenylpyruvate complexes, respectively.…”

Section: Enzymatic Assaymentioning

confidence: 99%

Characterization of aromatic aminotransferases from the hyperthermophilic archaeon Thermococcus litoralis

Andreotti

Cubellis

Nitti

et al. 1994

European Journal of Biochemistry

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The hyperthermophilic archaeon (formerly archaebacterium) Thermococcus litoralis grows at temperatures up to 98°C using peptides and proteins as the sole sources of carbon and nitrogen. Cell-free extracts of the organism contained two distinct types of aromatic aminotransferases (EC 2.6.1.57) which were separated and purified to electrophoretic homogeneity. Both enzymes are homodimers with subunit masses of approximately 47 kDa and 45 kDa. Using 2-oxoglutarate as the amino acceptor, each catalyzed the pyridoxal-5'-phosphate-dependent transamination of the three aromatic amino acids but showed virtually no activity towards aspartic acid, alanine, valine or isoleucine. From the determination of K,,, and kc,, values using 2-oxoglutarate, phenylalanine, tyrosine and tryptophan as substrates, both enzymes were shown to be highly efficient at transaminating phenylalanine (kcar/K,,, =400 s-' mIv-') ; the 47-kDa enzyme showed more activity towards tyrosine and tryptophan compared to the 45-kDa one. Kinetic analyses indicated a two-step mechanism with a pyridoxamine intermediate. Both enzymes were virtually inactive at 30°C and exhibited maximal activity between 95-100°C. They showed no N-terminal sequence similarity with each other (-30 residues), nor with the complete amino acid sequences of aromatic aminotransferases from Escherichia coli and rat liver. The catalytic properties of the two enzymes are distinct from bacterial aminotransferases, which have broad substrate specificities, but are analogous to two aromatic aminotransferases which play a biosynthetic role in a methanogenic archaeon. In contrast, it is proposed that one or both play a catabolic role in proteolytic 7: litoralis in which they generate glutamate and an arylpyruvate. These serve as substrates for glutamate dehydrogenase and indolepyruvate ferredoxin oxidoreductase in a novel pathway for the utilization of aromatic amino acids.

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Brain Phenylalanine Aminotransferase: *

Cited by 27 publications

References 19 publications

Characterization of tryptophan aminotransferase 1 of Malassezia furfur, the key enzyme in the production of indolic compounds by M. furfur

Characterization of tryptophan aminotransferase 1 of Malassezia furfur, the key enzyme in the production of indolic compounds by M. furfur

Phenylalanine-pyruvate aminotransferase activity in chicks subjected to phenylalanine imbalance or phenylalanine toxicity

Characterization of aromatic aminotransferases from the hyperthermophilic archaeon Thermococcus litoralis

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