Phenyllactic acid is a metabolite of phenylalanine. Inborn errors of metabolism are genetic disorders that disrupt biochemical pathways in the body. These disorders are rare, but their effects can be devastating. Often, there is a defect in a gene that codes for a certain enzyme, causing the body to either produce malfunctioning enzymes or none of the enzymes at all. These missing or malfunctioning enzymes prevent important biochemical reactions from occurring and cause metabolites (including organic acids) to accumulate. For example, one of the better known inborn errors of metabolism is phenylketonuria (PKU). In PKU, there is a defect in the gene for phenylalanine hydroxylase (PAH), which is responsible for converting the amino acid phenylalanine to tyrosine. When PAH isn’t working properly, the body tries to metabolize phenylalanine through an alternative pathway, and organic acids like phenyllactate and phenylacetate are produced as a result.

References:

- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2423317/