Question

Identify the correct combinations.

	Substrate	Enzyme	Product
I	Phosphoenol pyruvate	PEP carboxylase	$C_4$ acid
II	Malate	Malic enzyme	$C_4$ acid
III	RuBP	Ribulose phosphate kinase	$C_3$ acid
IV	Pyruvate	Pyruvate dikinase	$C_3$ acid

• A. III and IV
• B. I and IV
• C. II and III
• D. I and II

Answer 1

Answer: (B)

I and IV

I. In C${}_4$ cycle, during primary carboxylation of phosphoenolpyruvate (PEP) to form oxaloacetic acid (a 4 carbon compound), the presence of enzyme phosphoenol carboxylase (PEP carboxylase) is required.

II. In bundle sheath chloroplasts, the malate is decarboxylated to yield pyruvic acid (a 3 carbon compound) and CO${}_2$ in presence of the malic enzyme.

III. In the Calvin cycle, carboxylation of RuBP to form 3- phosphoglycerate (PGA, 3 carbon compound) in presence of ribulose biphosphate carboxylase (RUBISCO).

IV. The pyruvate formed by the decarboxylation converted to phosphoenolpyruvate (3 carbon compound) in presence of enzyme pyruvate phosphate dikinase.

Hence, the correct answer is 'I and IV'.