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L-phenylalanin: Most amino acids, with the exception of glycine, can appear in two forms called the D- and L- forms. Each form is a reversed mirror image of the other. Amino acids in the L- form are the natural form of amino acids found in living plant and animal tissues, and are considered to be more compatible to human biochemistry than the D- forms. All amino acids used in human protein structures are of the L- form, with the exception of phenylalanine, which can also appear as DL-phenylalanine.
Phenylalanine comes in two forms which are mirror images of each other:
Phenylalanine activity is enhanced by additional Vitamin B6, especially in studies on depression. Phenylalanine deficiency can cause bloodshot eyes, cataracts and behavioral changes. It is one of the amino acids which the body cannot manufacture itself, but must acquire from food. It is abundant in meats and cheese. Phenylalanine is a precursor of tyrosine, and together they lead to the formation of thyroxine or thyroid hormone, and of epinephrine and norepinephrine which is converted into a neurotransmitter used by the brain to manufacture norepinephrine which promotes mental alertness, memory, elevates mood, and suppresses the appetite very effectively.
Rhodotorula glutinis is a convenient source of L-phenylalanine ammonia-lyase, an enzyme that is useful as a biochemical reagent in the assay of L-phenylalanine. There have been previous descriptions of induced lyase production in complex medium where induction occurs late in exponential growth, suggesting a role in secondary metabolism such as is the case in higher plants. A higher specific activity of L-phenylalanine ammonia-lyase (sixfold higher than a complex medium) can be obtained during midexponential growth in a defined medium containing L-phenylalanine as the sole source of carbon. L-Phenylalanine will also induce lyase synthesis during exponential growth in minimal in which L-phenylalanine is the sole source of nitrogen. The appearance of lyase in complex medium supplemented with L-phenylalanine is probably triggered fortuitously by exhaustion late in growth of a prime source of nitrogen. In this study, R. glutinis appeared to express a single lyase enzyme, regardless of whether induction was nitrogen signaled or carbon signaled. Thin-layer chromatographic analysis of ether extracts prepared from cultures induced with doubly labeled (U-14C; ring-4-3H) L-phenylalanine provided evidence of a catabolic sequence containing cinnamic acid, benzoic acid, and 4-hydroxybenzoic acid as degradative intermediates. 3,4-Dihydroxybenzoic acid was not identified as a catabolic intermediate.