Alkaptonuria is due to deficiency of

(D) Homogentisic acid oxidase # Enzyme defect in Ochronosis (Alkaptonuria):> Defective enzyme in alkaptonuria is Homogentisate oxidase in tyrosine metabolism.> Homogentisate accumulates in tissues and blood, and is excreted into urine.> Homogentisate, on standing, gets oxidized to the corresponding quinones, which polymerize to give black or brown colour.> For this reason, the urine of alkaptonuric patients resembles coA are in colour.> Homogentiste gets oxidised by polyphenol oxidase to benzoquinone acetate which undergoes polymerization to form a pigment "Alkapton".> Alkapton gets deposited in connective tissues, bones and various organs resulting in a condition called "Ochronosis".> Many patients suffer from arthritis: and this is believed to be due to the deposition of pigment alkapton in the connective tissues.