Protein phenylalanine free

Hereditary tyrosinaemia type II is caused by a deficiency of tyrosine aminotransferase, leading to eye lesions, skin lesions and neurological complications. The aim of dietary management is to prevent the accumulation of tyrosine and phenylalanine by a low-protein diet. The protein requirements are met by supplementing the diet with a tyrosine- and phenylalanine-free amino acid mixture. 

XPHEN TYR Maxamum and TYR express are proprietary tyrosine- and phenylalanine-free powdered drink mixes suitable for children over 8 years, teenagers and adults, including pregnant women (Table 41.5). For a 25kg child around 8 years requiring 2g protein/kg/day and with no source of protein or iodide other than tyrosine-and phenylalanine-free drinks, the daily iodide intakes are around 137 rg/day of iodine, which are higher than current... 

Protein recommendations for individuals consuming phenylalanine-free amino acid-based medical foods as part of their protein source... 

Subtract me protein provided by me standard infant formula from me infant s total protein needs. Calculate amount of phenylalanine-free medical food required to meet me ronaining protein needs. 

A wide variety of medical foods are available for those over age 2. Most clinics transition from a complete medical food designed for infants to one designed for toddlers and children. These products provide carbohydrate, fat, and micronutrients, in addition to phenylalanine-free amino acids. However, some medical foods designed for older age groups contain little or no fat, and others are concentrated in protein with little fat or carbohydrate. These medical foods can meet protein needs with a smaller volume and are often used for those requiring a lower energy formula. 

The versatility of the plastein reaction is also demonstrated by examples wherein undesired amino acids are removed from a protein. A phenylalanine-free diet, which can be prepared by mixing amino acids, is recommended for certain metabolic defects. However, the use of a phenylalanine-free higher molecular weight peptide is more advantageous with respect to sensory and osmotic properties. Such peptides can be prepared from protein by the plastein reaction. First, the protein is partially hydrolyzed with pepsin. Treatment with pronase under... 

Phenylalanine residues in proteins and free phenylalanine are oxidised by various reactive oxygen species to 2- and 3-hydroxy derivatives, and possibly other products too. 

Pish protein concentrate and soy protein concentrate have been used to prepare a low phenylalanine, high tyrosine peptide for use with phenylketonuria patients (150). The process includes pepsin hydrolysis at pH 1.5 ptonase hydrolysis at pH 6.5 to Hberate aromatic amino acids gel filtration on Sephadex G-15 to remove aromatic amino acids incubation with papain and ethyl esters of L-tyrosine and L-tryptophan, ie, plastein synthesis and ultrafiltration (qv). The plastein has a bland taste and odor and does not contain free amino acids. Yields of 69.3 and 60.9% from PPG and soy protein concentrate, respectively, have been attained. 

Now, we will consider the major reactions of peroxynitrite with biomolecules. It was found that peroxynitrite reacts with many biomolecules belonging to various chemical classes, with the bimolecular rate constants from 10-3 to 10s 1 mol 1 s 1 (Table 21.2). Reactions of peroxynitrite with phenols were studied most thoroughly due to the important role of peroxynitrite in the in vivo nitration and oxidation of free tyrosine and tyrosine residues in proteins. In 1992, Beckman et al. [112] have showed that peroxynitrite efficiently nitrates 4-hydroxyphenylacetate at pH 7.5. van der Vliet et al. [113] found that the reactions of peroxynitrite with tyrosine and phenylalanine resulted in the formation of both hydroxylated and nitrated products. In authors opinion the formation of these products was mediated by N02 and HO radicals. Studying peroxynitrite reactions with phenol, tyrosine, and salicylate, Ramezanian et al. [114] showed that these reactions are of first-order in peroxynitrite and zero-order in phenolic compounds. These authors supposed that there should be two different intermediates responsible for the nitration and hydroxylation of phenols but rejected the most probable proposal that these intermediates should be NO2 and HO. ... 

The same type of entropic effect plays a major role in directing the folding of globular proteins. About half of the amino acid side chains in proteins are hydrophobic (e.g., alanine, valine, isoleucine, leucine, and phenylalanine). Entropic effects strongly favor internal locations for these side chains where they are free from contacts with water (e.g., see fig. 1.12, which shows the location of polar and apolar side chains in cytochrome c). 

Kaur H, Fagerheim I, Grootveld M, Puppo A, Halliwell B (1988) Aromatic hydroxylation of phenylalanine as an assay for hydroxyl radicals application to activated human neutrophils and to the heme protein leghemoglobin. Anal Biochem 172 360-367 Kaur H, Whiteman M, Halliwell B (1997) Peroxynitrite-dependent aromatic hydroxylation and nitration of salicylate and phenylalanine. Is OH radical involved Free Rad Res 26 71-82... 

Enzymatic hydrolysates of various proteins have a bitter taste, which may be one of the main drawbacks to their use in food. Arai el al. [90] showed that the bitterness of peptides from soybean protein hydrolysates was reduced by treatment of Aspergillus acid carboxypeptidase from A. saitoi. Significant amounts of free leucine and phenylalanine were liberated by Aspergillus carboxypeptidase from the tetracosapeptide of the peptic hydrolysate of soybean as a compound having a bitter taste. Furthermore, the bitter peptide fractions obtained from peptic hydrolysates of casein, fish protein, and soybean protein were treated with wheat carboxypeptidase W [91], The bitterness of the peptides lessened with an increase in free amino acids. Carboxypeptidase W can eliminate bitter tastes in enzymatic proteins and is commercially available for food processing. 

---