The enzyme phenylalanine racemase (, ''phenylalanine racemase'', ''phenylalanine racemase (adenosine triphosphate-hydrolysing)'', ''gramicidin S synthetase I'') is the enzyme that acts on amino acids and derivatives. It activates both the L & D stereo isomers of phenylalanine to form L-phenylalanyl adenylate and D-phenylalanyl adenylate, which are bound to the enzyme. These bound compounds are then transferred to the thiol group of the enzyme followed by conversion of its configuration, the D-isomer being the more favorable configuration of the two, with a 7 to 3 ratio between the two isomers. The racemisation reaction of phenylalanine is coupled with the highly favorable hydrolysis of
adenosine triphosphate (ATP) to
adenosine monophosphate (AMP) and
pyrophosphate (PP), thermodynamically allowing it to proceed. This reaction is then drawn forward by further hydrolyzing PP to inorganic phosphate (P
i), via
Le Chatelier's principle.
Other names
*phenylalanine racemase
*phenylalanine racemase (adenosine triphosphate-hydrolysing)
*gramicidin S synthetase I
Pathway
* Phenylalanine Metabolism
Substrate
* L –
Phenylalanine
Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino a ...
Product
* D - Phenylalanine
Cofactor
*
Pyridoxal-phosphate (active form of vitamin B
6)
Links to disease
Problems in the digestion of
phenylalanine
Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino a ...
(phe) to
tyrosine (tyr) lead to the buildup of both phe and phenylpyruvate, in a disease called
Phenylketonuria (PKU). These two compounds build up in the blood stream and cerebral spinal fluid, which can lead to mental retardation if left untreated. Treatment consists of a restricted diet of foods that contain phe or compounds that can breakdown into phe. Children in the US are routinely tested for this at birth. For more information see the
Phenylketonuria page or the link below.
Quick facts
* pH Range = 7.2 – 8.6
* Equilibrium Ratio:
L-Phe:D-Phe = 3:7
* Specific Activity: 0.019
The reaction
See also
*
Phenylalanine
Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino a ...
*
Racemase Epimerases and racemases are isomerase enzymes that catalyze the inversion of stereochemistry in biological molecules.
Racemases catalyze the stereochemical inversion around the asymmetric carbon atom in a substrate having only one center of asymm ...
*
Phenylketonuria
References
*
*
External links
* Protein Data Bank 1am
{{Enzymes
Metabolism
EC 5.1.1