The Phenylalanine Hydroxylating System from Mammalian Liver

Kaufman, Seymour

doi:10.1002/9780470122808.ch6

Cited by 72 publications

(24 citation statements)

References 94 publications

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“…However this seems unlikely since the manufacturing technology of this RP-Phe was the same as the RP-Lys product evaluated in Sakkers et al (2013) which was measured in vivo to have a rumen escape of 52% of consumed Lys. Haque et al (2013) (Kaufman 1971), the first step in catabolizing Trp to synthesize serotonin and, since Trp levels in the plasma of both Phe supplemented treatments decreased vs.…”

Section: Discussionmentioning

confidence: 99%

Effects of ruminally protected methionine and/or phenylalanine on performance of high producing Holstein cows fed rations with very high levels of canola meal

Swanepoel

Robinson

Erasmus

2015

Animal Feed Science and Technology

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Canola meal is the second largest protein feed in the Northern latitudes and inclusion levels in dairy rations are expected to increase due to projected large increases in production of canola seed in Canada. However, a recent study (Swanepoel et al. 2014) showed that even though higher inclusions of canola meal (CM) had a positive effect on production when CM directly substituted for high protein corn based dried distillers grains (DDG), that there was an optimum point at 120 to 135 g/kg of diet dry matter (DM) after which animal performance seemed to decline. Only the amino acids (AA), methionine (Met), phenylalanine (Phe) and leucine (Leu) could have limited production based upon plasma AA concentrations at the highest CM inclusion Addition of Phe to the Met supplementation changed the way energy was utilized by the cows, redirecting energy liberated by Met from milk components toward BCS gain. It remains unclear if Phe was limiting in the Control ration or if RP Phe was not fed at high enough levels to have a measurable response on production. However, it is clear that AA limitations, requirements and production responses are governed by much more than plasma AA levels. Results further suggest that AA are bioactive metabolites to the extent that they can change animal performance, even when they are not "limiting" per se, and that their supplementation to practical dairy cattle diets should be approached with extreme caution for this reason.

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Section: Discussionmentioning

confidence: 99%

Effects of ruminally protected methionine and/or phenylalanine on performance of high producing Holstein cows fed rations with very high levels of canola meal

Swanepoel

Robinson

Erasmus

2015

Animal Feed Science and Technology

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“…Recently, we sequenced the whole genome of Mortierella alpina (ATCC 32222) (21), and our analysis suggested that there are two putative copies of the BH 4 -dependent PAH gene for the catabolism of phenylalanine in M. alpina. Genes encoding PCD and DHPR, which are required for the regeneration of BH 4 , an essential component of the phenylalanine-hydroxylating system (6), were also found in the M. alpina genome. The BH 4 de novo synthesis pathway in M. alpina was first purified and characterized in our laboratory (22), but the function of BH 4 in fungi is still not well understood.…”

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confidence: 99%

“…Genes encoding PCD and DHPR, which are required for the regeneration of BH 4 , an essential component of the phenylalanine-hydroxylating system (6), were also found in the M. alpina genome. The BH 4 de novo synthesis pathway in M. alpina was first purified and characterized in our laboratory (22), but the function of BH 4 in fungi is still not well understood. The presence of the phenylalanine-hydroxylating system in M. alpina suggests that fungi can make use of the system in their phenylalanine degradation strategy.…”

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confidence: 99%

“…The animal phenylalanine-hydroxylating system consists of several essential components: phenylalanine hydroxylase (PAH) (EC 1.14.16.1), pterin-4␣-carbinolamine dehydratase (PCD) (EC 4.2.1.96), dihydropteridine reductase (DHPR) (EC 1.5.1.34), and the obligatory cofactors tetrahydrobiopterin (BH 4 ) and molecular oxygen (3,4) (Fig. 1).…”

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confidence: 99%

“…PAH is one of the BH 4 -dependent aromatic amino acid hydroxylases, which also include tryptophan hydroxylase (TrpOHase) (EC 1.14.16.4) and tyrosine hydroxylase (TyrOHase) (EC 1.14.16.2) (5). BH 4 is regenerated following PAH-mediated phenylalanine hydroxylation by two additional enzymes, PCD and DHPR ( Fig. 1) (6).…”

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confidence: 99%

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Role of the Phenylalanine-Hydroxylating System in Aromatic Substance Degradation and Lipid Metabolism in the Oleaginous Fungus Mortierella alpina

Wang

Chen

Hao

et al. 2013

Appl Environ Microbiol

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c Mortierella alpina is a filamentous fungus commonly found in soil that is able to produce lipids in the form of triacylglycerols that account for up to 50% of its dry weight. Analysis of the M. alpina genome suggests that there is a phenylalanine-hydroxylating system for the catabolism of phenylalanine, which has never been found in fungi before. We characterized the phenylalanine-hydroxylating system in M. alpina to explore its role in phenylalanine metabolism and its relationship to lipid biosynthesis. Significant changes were found in the profile of fatty acids in M. alpina grown on medium containing an inhibitor of the phenylalanine-hydroxylating system compared to M. alpina grown on medium without inhibitor. Genes encoding enzymes involved in the phenylalanine-hydroxylating system (phenylalanine hydroxylase [PAH], pterin-4␣-carbinolamine dehydratase, and dihydropteridine reductase) were expressed heterologously in Escherichia coli, and the resulting proteins were purified to homogeneity. Their enzymatic activity was investigated by high-performance liquid chromatography (HPLC) or visible (Vis)-UV spectroscopy. Two functional PAH enzymes were observed, encoded by distinct gene copies. A novel role for tetrahydrobiopterin in fungi as a cofactor for PAH, which is similar to its function in higher life forms, is suggested. This study establishes a novel scheme for the fungal degradation of an aromatic substance (phenylalanine) and suggests that the phenylalaninehydroxylating system is functionally significant in lipid metabolism.

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Measurement of Oxygen Consumption by the Spectrophotometric Oxyhemoglobin Method

Bârzu

1984

Methods of Biochemical Analysis

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The Phenylalanine Hydroxylating System from Mammalian Liver

Cited by 72 publications

References 94 publications

Effects of ruminally protected methionine and/or phenylalanine on performance of high producing Holstein cows fed rations with very high levels of canola meal

Effects of ruminally protected methionine and/or phenylalanine on performance of high producing Holstein cows fed rations with very high levels of canola meal

Role of the Phenylalanine-Hydroxylating System in Aromatic Substance Degradation and Lipid Metabolism in the Oleaginous Fungus Mortierella alpina

Measurement of Oxygen Consumption by the Spectrophotometric Oxyhemoglobin Method

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