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Phenylalanine is structurally closely related to dopamine, epinephrine (adrenaline) and tyrosine. It is a direct precursor to the neuromodulator phenylethylamine a commonly used dietary supplement.

Individuals with this disorder are known as "phenylketonurics" and must abstain from consumption of too much phenylalanine.

This compound, sold under the trade names "Equal" and "NutraSweet", is metabolized by the body into several chemical byproducts including phenylalanine. The breakdown problems phenylketonurics have with protein and the attendant build up of phenylalanine in the body also occurs with the ingestion of aspartame, although to a lesser degree. Accordingly, all products in Australia, the U.S. and Canada that contain aspartame must be labeled: "Phenylketonurics: Contains phenylalanine." In the UK, foods containing aspartame must carry ingredient panels that refer to the presence of "aspartame or E951" Aspartame , Food Standards Agency and they must be labeled with a warning "Contains a source of phenylalanine." These warnings are specifically placed to aid individuals who suffer from PKU so that they can avoid such foods.

The biological functions of D -amino acids remain unclear although some, such as D -phenylalanine, may have pharmacological activity.

The reputed analgesic activity of DL-phenylalanine may be explained by the possible blockage by D -phenylalanine of enkephalin degradation by the enzyme carboxypeptidase A. Christianson DW, Mangani S, Shoham G, Lipscomb WN. "Binding of D-phenylalanine and D-tyrosine to carboxypeptidase A." Journal of Biological Chemistry 1989 Aug 5;264(22):12849-53.

A small amount of D -phenylalanine appears to be converted to L -phenylalanine.

It appears to cross the blood-brain barrier less efficiently than L -phenylalanine, and so a small amount of an ingested dose of D -phenylalanine is not absorbed but excreted in the urine.

Heinrich Matthaei and Marshall W. Nirenberg in 1961. They showed that by using m -RNA to insert multiple uracil repeats into the bacterium E. coli , the bacterium produced a new protein consisting solely of repeated phenylalanine amino acids. This discovery led to the determination of the relationship between RNA and amino acids, which was fundamental to the understanding of the Genetic Code.

Source: Wikipedia > Phenylalanine