A patient complains of knee pain. Routine investigations are unremarkable and still, the patient is unsatisfied. Urine turns black on standing, what is the enzyme involved?
Homogentisate oxidase
Xanthine oxidase
Methyl malonate oxidase
Phenyl pyruvate oxidase
Alkaptonuria - Due to deficiency of Homogentisate dioxygenase/ oxidase (requires Iron) Fresh urine is normal in colour On standing or on exposure to air - turns Black - Homogentisic acid accumulated - get oxidised - gives rise to Black urine - Homogentisic acid gets polymerized in body forming ALKAPTON BODIES, which gets accumulated in: Cailages - Nose, ear pinna, interveebral disc Connective tissue has bluish black colour. Patient develops ahralgia & ahritis. - This condition is known as Ochronosis. Ahritis is also known as ochronotic ahritis - Benedict 's test is positive due to homogentisic Acid, which is a Reducing substance - Treatment drug is NITISINONE
NEET Jan 2020