Sucrose-phosphate synthase (SPS) and sucrose-phosphate phosphatase (SPP) are two key enzymes involved in the biosynthesis of sucrose. Following are certain statements regarding these two enzymes:

A. Fructose-6-phosphate is one of the substrates of SPS enzyme.

B. Fructose-6-phosphate and UDP-glucose are the substrates of SPP enzyme.

C. Sucrose is the final product of SPP enzyme.

D. UDP is one of the products of SPS enzyme while Pi is one of the products of SPP enzyme.

Which one of the following options represents the combination of all correct statements

Correct option is C

Explanation:

The synthesis of sucrose in plants involves two key enzymatic steps catalyzed by:

1. Sucrose-phosphate synthase (SPS)
2. Sucrose-phosphate phosphatase (SPP)

These enzymes act sequentially to produce sucrose from precursor metabolites such as fructose-6-phosphate (F6P) and UDP-glucose.

Statement-wise Analysis:

1. Statement A: Correct 

   • Fructose-6-phosphate (F6P) is one of the substrates of the SPS enzyme.
   • The SPS enzyme catalyzes the reaction:$$Fructose-6-phosphate+UDP-glucose\to Sucrose-6-phosphate+UDP$$
     

2. Statement B: Incorrect 

   • Fructose-6-phosphate and UDP-glucose are substrates for SPS, not SPP.
   • The SPP enzyme acts on sucrose-6-phosphate to remove the phosphate group and form sucrose.
   • Therefore, this statement is incorrect because it misassigns the substrates of SPS to SPP.

3. Statement C: Correct 

   • Sucrose is the final product of the SPP enzyme, which catalyzes:$$Sucrose-6-phosphate\to Sucrose+Pi$$
     

4. Statement D: Correct 

   • The SPS enzyme produces UDP (uridine diphosphate) as a byproduct.
   • The SPP enzyme produces inorganic phosphate (Pi) when it cleaves sucrose-6-phosphate.
     

Information Booster:

1. SPS (Sucrose-Phosphate Synthase) is a key regulatory enzyme in sucrose biosynthesis.
2. SPP (Sucrose-Phosphate Phosphatase) converts sucrose-6-phosphate to sucrose.
3. SPS is regulated by allosteric modulators and phosphorylation-dephosphorylation.
4. Sucrose is transported in phloem and is a primary transport form of carbon in plants.
5. UDP-glucose is a common glucose donor in various biosynthetic reactions.
6. SPP ensures the removal of phosphate group, making sucrose stable and ready for transport.
7. The biosynthesis pathway is critical during active photosynthesis and carbohydrate storage.