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A LOW‐PHENYLALANINE, HIGH‐TYROSINE PLASTEIN AS AN ACCEPTABLE DIETETIC FOOD. Method of Preparation by Use of Enzymatic Protein Hydrolysis and Resynthesis
Author(s) -
YAMASHITA MICHIKO,
ARAI SOICHI,
FUJIMAKI MASAO
Publication year - 1976
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1976.tb14382.x
Subject(s) - chemistry , phenylalanine , hydrolysis , papain , tyrosine , amino acid , chromatography , hydrolysate , sephadex , tryptophan , enzymatic hydrolysis , aromatic amino acids , pronase , biochemistry , enzyme , trypsin
A method was proposed to prepare a peptide‐type low‐phenylalanine, high‐tyrosine food for curing phenylketonuria. A fish protein concentrate (FPC) and a soybean protein isolate (SPI) were used as starting materials. Each was limitedly hydrolyzed with a very small amount of pepsin The peptic hydrolysate was further hydrolyzed with Pronase under an unconventional pH‐condition to liberate aromatic amino acids. These were removed by Sephadex G‐15 with the aid of its adsorp tion activity. To the resulting aromatic amino acid‐free fraction were added ethyl esters of L‐tyrosine and L‐tryptophan and the mixture was incubated with papain under such conditions as its reverse process called “plastein synthesis reaction” proceeded efficiently. The reaction product was treated by ultrafiltration to obtain a plastein as a fraction having the lowest molecular weight of 500. The yields were 69.3% from FPC and 60.9% from SPI. Phenylalanine, tyrosine and tryptophan contents were 0.05%, 7.82% and 2.98% in the FPC plastein and 0.23%, 7.69% and 2.80% in the SPI plastein. Each plastem did not contain any free amino acids and was almost completely flat in taste and odor.