<prompt> In Ochronosis there is deficiency of which of the following enzymes?Phenylalanine decarboxylaseHomogentisic acid oxidaseAlpha ketoglutarate decarboxylaseGlucocerebrosidase  <response>: The defective enzyme in Ochronosis Alkaptonuria is homogentisic acid oxidase in tyrosine metabolism. Homogentisate 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 condition called OCHRONOSIS. 