This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: nutrition and digestion, Subject name: Biochemistry
Zinc is an essential component of the following enzymes except 
Select and explain. 
A. Carbonic anhydrase, B. Alkaline phosphate, C. Xanthine oxidase, D. Ethanol dehydrogenase
C: Xanthine oxidase
Answer: C: Xanthine oxidase 
Explanation: Xanthine oxidase and aldehyde oxidase contain molybdoprotein, a substituted pterin to which molybdenum is bound by two sulfur atoms. Mo deficiency causes depression of xanthine oxidase activity, increased excretion of xanthine and decreased uric acid excretion.Ref: DM Vasudevan, page no: 430