4-Hydroxyphenylpyruvate dioxygenase (HPPD) is an important enzyme involved in the degradation pathway of tyrosine, catalyzing the conversion of 4-hydroxyphenylpyruvate to homogentisic acid. HPPD belongs to the non-heme iron-dependent dioxygenase family and possesses specific iron-binding sites. The enzyme is expressed in tissues such as the liver and is crucial for amino acid degradation and energy metabolism. HPPD has also been found in plants and microorganisms, participating in biosynthetic and metabolic pathways. Gene-specific expression varies in different organisms and tissues, and mutations may lead to metabolic disorders such as HPPD deficiency, affecting the normal metabolism of tyrosine and potentially causing skin and eye sensitivity.