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Proteins and Proteomics
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
Essential amino acids are called essential not because they are more important than the others, but because the body does not synthesize them, making it essential to include them in one’s diet to obtain them. On the other hand, the amino acids arginine, cysteine, glycine, glutamine, histidine, proline, serine, and tyrosine are considered conditionally essential, meaning they are not normally required in the diet but must be supplied exogenously to specific populations who do not synthesize them in adequate amounts. For example, individuals living with phenylketonuria (PKU) disease must keep their intake of phenylalanine extremely low to prevent mental retardation and other metabolic complications. However, phenylalanine is the precursor for tyrosine synthesis. Without phenylalanine, tyrosine cannot be made and so tyrosine becomes essential in the diet of PKU patients.
Proteins and proteomics
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
Essential amino acids are called essential not because they are more important than the others, but because the body does not synthesize them, making it essential to include them in one’s diet in order to obtain them. On the other hand, the amino acids arginine, cysteine, glycine, glutamine, histidine, proline, serine, and tyrosine are considered conditionally essential, meaning they are not normally required in the diet, but must be supplied exogenously to specific populations who do not synthesize it in adequate amounts. For example, individuals living with phenylketonuria (PKU) disease must keep their intake of phenylalanine extremely low to prevent mental retardation and other metabolic complications. However, phenylalanine is the precursor for tyrosine synthesis. Without phenylalanine, tyrosine cannot be made and so tyrosine becomes essential in the diet of PKU patients.
Regulation, ethics and values
Published in Emilie Cloatre, Martyn Pickersgill, Knowledge, Technology and Law, 2014
Emilie Cloatre, Martyn Pickersgill
To demonstrate how these thickets can evolve, and to exemplify the deeply unhelpful divides that are erected/perpetuated, we consider one particular undertaking: the ambition to conduct research using newborn bloodspot collections, or so-called ‘Guthrie cards’. Newborn screening programmes began in many western countries in the 1960s. They involve a heel-prick sample of blood from the infant that is retained on manual cards. Blood samples are initially taken in the health interests of the infant to diagnose and treat conditions that can be detected and eradicated or effectively managed at this early stage of life (e.g. phenylketonuria (PKU) or hypothyroidism). It was common to retain these cards, however, and their value has grown over the decades both with advances in genetic analysis and with the prospect of effective linkage to medical and other records (Couzin-Frankel, 2009).
Gene Editing: A View Through the Prism of Inherited Metabolic Disorders
Published in The New Bioethics, 2018
The inherited metabolic disorders arise when a mutation in a given gene results in a deficiency of the related enzyme. The majority of these conditions are inherited in an autosomal recessive manner, whereby both the maternally inherited and paternally inherited copy of the given gene must harbour a mutation for the disease to manifest. In the usual situation this means that both parents are heterozygous carriers of the condition, i.e. they each carry one mutated copy of the gene and one ‘healthy’ copy. Thus a deficiency of the enzyme phenylalanine hydroxylase caused by mutations in the PAH gene gives rise to the condition phenylketonuria (PKU), associated with pathologically high phenylalanine levels as this amino acid cannot be converted to tyrosine. Untreated, PKU results in significant progressive damage to the central nervous system, manifesting with microcephaly, developmental delay and significant cognitive impairment. PKU is eminently treatable with dietary phenylalanine restriction, and detection via newborn screening permits treatment to be commenced before damage occurs. Many of the metabolic disorders, however, carry a devastating prognosis, for example mucopolysaccharidosis type III (Sanfilippo syndrome) which is caused by deficiency of one of the several lysosomal enzymes that degrade complex macro-molecules (the glycosaminoglycans), with the result that these macro-molecules accumulate in different tissues of the body including the brain and cause a relentlessly progressive neurodegenerative disorder, with childhood onset dementia and significantly curtailed life-expectancy.