Hepatic Metabolism of Phenylalanine During Development*

Kenney, Francis T.; Kretchmer, Norman

doi:10.1172/jci103998

Cited by 38 publications

(6 citation statements)

References 22 publications

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“…The overall process may thus be controlled by enzymes operating at the initial steps of degradation. For example, various transaminases have been reported to develop activity in rat liver at the time of birth, including tyrosine transaminase (Auerbach & Waisman, 1959;Kretchmer, Levine, McNamara, & Barnett, 1956;, phenylalanine transaminase (Kenney & Kretchmer, 1959), tryp. tophan tranaminase (Trappit, 1964) and histidine transaminase (Makoff & Baldridge, 1964).…”

Section: Discussionmentioning

confidence: 99%

Gluconeogenesis from amino acids in neonatal rat liver

Yeung¹,

Oliver²

1967

Biochemical Journal

104

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1. The utilization of amino acids for gluconeogenesis by rat liver develops in postnatal life, reaching maximum activity at the fifth day. 2. The activity of aspartate transaminase shows a similar trend in postnatal development and the increased activity appears to be due to the soluble enzyme. 3. The activity of alanine transaminase is low in foetal and postnatal rat liver and increases in activity at about the twentieth day. 4. Aspartate, glutamate and alanine make a major contribution to gluconeogenesis in the postnatal rat liver.

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Section: Discussionmentioning

confidence: 99%

Gluconeogenesis from amino acids in neonatal rat liver

Yeung¹,

Oliver²

1967

Biochemical Journal

104

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“…Phenylketonuria is an autosomal recessive disorder characterized by lack of phenylalanine hydroxylase leading to accumulation of Phe in the circulation and mental retardation in childhood (3). Although phenylalanine hydroxylase activity in the adult range has been demonstrated in fetal liver after 8 weeks of gestation (4), a number of studies have suggested that the overall capacity of the enzyme system is limited in the fetus (5)(6)(7). Based on these observations in fetal livers, it has been hypothesized that Tyr is a conditionally essential amino acid for preterm infants (8).…”

mentioning

confidence: 99%

The kidney is an important site for in vivo phenylalanine-to-tyrosine conversion in adult humans: A metabolic role of the kidney

Møller

Meek

Bigelow

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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Synthesis of Tyr in the human body occurs by hydroxylation of the indispensable amino acid Phe. Until now, it was believed that in humans, this process was restricted to the liver, but we provide compelling evidence of production of Tyr from Phe in the kidney. To determine whether the human kidney produces Tyr, we measured Tyr balance, the Tyr appearance rate, and the Phe-to-Tyr conversion in 12 healthy human subjects by using [ 15 N]Phe and [ 2 H4]Tyr as tracers. Renal plasma flow was measured by using paraaminohippurate, and sampling from the femoral artery and renal veins was performed. The results were compared with those obtained in 12 control subjects undergoing hepatic vein catheterization and infusion of identical tracers. In all 12 subjects, there was a net uptake of Phe by the kidney (2.2 ؎ 1.2 mol͞min), whereas Tyr was released (5.3 ؎ 1.5 mol͞min). In contrast, there was a net uptake of both Phe (9.5 ؎ 1.2 mol͞min) and Tyr (14.3 ؎ 1.3 mol͞min) by the splanchnic bed. Phe conversion to Tyr occurred at a rate of 5.2 ؎ 1.2 mol͞min in kidney and 3.0 ؎ 0.7 mol͞min in the splanchnic bed. The kidney contributed a substantial amount of Tyr to the systemic circulation where the splanchnic bed was a net remover of Tyr. Our results demonstrate that the kidney is the major donor of Tyr to the systemic circulation by its conversion of Phe to Tyr. This observation may have important clinical implications for patients with both renal and hepatic disease, who may be at risk of Phe overloading and Tyr deficiency, and it should be considered when parenteral or enteral nutrients are administered rich in Phe and low in Tyr.

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“…The cofactor and dihydropteridine reductase were measured in foetal rat liver by Brenneman and Kaufman (1965), who found less activity than in the adult rat, whereas the hydroxylase activity was not diminished at all. Although Kenney and Kretchmer (1959) reported that the cofactor and dihydropteridine reductase were present in the foetal rat, they found that Phe p-hydroxylase activity was somewhat lower than in the adult. Recent work by McGee, Greengard, and Knox (1972) supports the latter finding.…”

Section: Discussionmentioning

confidence: 94%