Purine Nucleoside Phosphorylase: Physiology, Biochemistry, and Mechanism

The video explores purine catabolism, focusing on the degradation of adenosine to inosine and hypoxanthine. It details the role and mechanism of purine nucleoside phosphorylase, including its substrates and reaction steps. The video also discusses the impact of arsenate on enzyme activity and its detoxification process, highlighting the enzyme's ability to reduce arsenate to arsenite.

What is the initial molecule in the degradation pathway of adenosine?

• Xanthine

• Hypoxanthine

• Adenosine monophosphate

• Inosine

Which enzyme is responsible for the conversion of inosine to hypoxanthine?

• Xanthine oxidase

• Phosphoglucomutase

• Purine nucleoside phosphorylase

• Adenosine deaminase

Which of the following is NOT a substrate for purine nucleoside phosphorylase?

• Deoxyadenosine

• Cytosine

• Xanthine

• Inosine

What type of reaction sequence occurs in purine nucleoside phosphorylase?

• SN1

• E2

• SN2

• E1

What is the end product of purine degradation in humans?

• Xanthine

• Inosine

• Urate

• Hypoxanthine

Which enzyme converts hypoxanthine to xanthine?

• Adenosine deaminase

• Purine nucleoside phosphorylase

• Xanthine oxidase

• Phosphoglucomutase

What can cause the uncoupling of reactions in purine nucleoside phosphorylase?

• Phosphate deficiency

• Arsenate poisoning

• Excess hypoxanthine

• Lack of ribose

What is the role of lipoate in purine nucleoside phosphorylase?

• Acts as a substrate

• Detoxifies arsenate

• Converts inosine to hypoxanthine

• Inhibits the enzyme

Which molecule is reduced to arsenite by purine nucleoside phosphorylase?

• Arsenate

• Phosphate

• Xanthine

• Hypoxanthine

What is the final product of xanthine oxidase activity?

• Inosine

• Ribose

• Hypoxanthine

• Urate