People with phenylketonuria must avoid foods containing the lowcalorie sweetener Aspartame, also known as NutraSueet. Find the structure of Aspartame in the Merck Index (or other scientific source) and state why these people must avoid this substance.

Phenylketonuria, commonly known as PKU, is a genetic metabolic disorder characterized by the deficiency of the enzyme phenylalanine hydroxylase. This enzyme is crucial for the normal processing of the amino acid phenylalanine, one of the building blocks of proteins. People with PKU have varying levels of enzyme deficiency, leading to an accumulation of phenylalanine in their body, which can cause a range of health issues, including intellectual disabilities and neurological problems if left untreated.

Newborns are routinely screened for PKU through a blood test so that they can be put on a phenylalanine-restricted diet if necessary. This diet is the main form of management for individuals with PKU, allowing them to lead healthy lives despite their inability to break down this specific amino acid effectively.

Aspartame is a low-calorie artificial sweetener used as a sugar substitute in many foods and beverages. Chemically, it is composed of two amino acids, phenylalanine and aspartic acid, combined through a methyl ester bond. The sweetener is approximately 200 times sweeter than sugar, which means only small amounts are needed to achieve the desired sweetness. Upon ingestion, aspartame is metabolized in the body, breaking down into its component parts, including phenylalanine. This is why its intake can be problematic for individuals with PKU since their bodies are unable to properly metabolize excess phenylalanine.

Amino acids are organic molecules that serve as the basic building blocks of proteins, which are essential to every cell and function in our bodies. There are 20 standard amino acids that combine in various sequences to form the diverse array of proteins necessary for life. Each amino acid features a central carbon atom bonded to a hydrogen atom, an amino group, a carboxyl group, and a unique side chain known as an R-group, which determines the amino acid's properties and role within proteins.

In biochemistry, the structure, role, and interaction of amino acids within proteins are fundamental for understanding how biological processes occur. Even slight changes in the amino acid composition of a protein can have significant effects on health, as seen with the accumulation of phenylalanine in individuals with PKU.

Diet plays a critical and often personalized role in managing genetic disorders. Many of these conditions, such as PKU, involve the malfunction of specific metabolic pathways, frequently those responsible for processing certain types of nutrients. For individuals with such disorders, strict adherence to a diet that limits the intake of problematic nutrients is essential to prevent complications and promote optimal health.

In the case of PKU, this means a diet low in phenylalanine, found in high-protein foods and certain sweeteners like aspartame. Regular monitoring and diet adjustments are typically coordinated with healthcare providers and dietitians to ensure that nutritional needs are met, especially in growing children, without causing harm from excess phenylalanine.