Individuals with
phenylketonuria (PKU) cannot metabolize
phenylalanine (Phe) and must adhere to a low-Phe diet in which most
dietary protein is provided by a Phe-free
amino acid formula.
Glycomacropeptide (GMP) is the only naturally occurring
protein that does not contain Phe, and is of interest as a source of
protein for dietary management of PKU. However, commercially available GMP contains too much Phe from residual
whey proteins and does not contain adequate levels of all the indispensable
amino acids to provide a nutritionally complete
protein. The aim of this study was to increase purity of GMP and develop a mass balance calculation for indispensable
amino acid supplementation of GMP foods.
Cation exchange chromatography, ultrafiltration/diafiltration, and lyophilization were used at the pilot plant scale to decrease Phe. Enough purified GMP (5 kg) was manufactured to provide 15 PKU subjects with a 4-d diet in which the majority of
protein was from GMP foods. A mass balance was used to supplement GMP foods so that all indispensable
amino acids met or exceeded the daily recommended intake. GMP foods were tested in a human clinical trial as a replacement for the traditional
amino acid formula. Nutritionally complete GMP foods created with high purity GMP provide individuals with PKU with more options to manage PKU, which may lead to improved compliance and quality of life.