Question

During the mineralization of the organic P compound, microorganisms cleave the compound by the production the enzymes:
(A). ATP sulfurylase
(B). Phosphatase
(C). Phytase
(D). Nitrogenase
Choose the correct answer from the options given below:

• (A) and (D) only.
• (B) and (D) only.
• (B) and (C) only.
• (C) and (D) only.

Hint:

Remember that "phytate" is the most dominant organic P source in soils, and "phytase" is the specific enzyme that degrades it.
Phosphatase is the general enzyme for organic P mineralization.
Both enzymes have the suffix "-ase," which indicates their biochemical catalytic role.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Soil organic phosphorus (P) accounts for a significant fraction of the total phosphorus in agricultural soils.
This pool is composed of various organic compounds, such as phytates, phospholipids, and nucleic acids.
Plants cannot directly absorb organic phosphorus; hence, it must undergo mineralization to be converted into orthophosphates (\( \text{H}_2\text{PO}_4^- \) and \( \text{HPO}_4^{2-} \)), which are highly bioavailable to plant roots.
Soil microorganisms play a crucial role in this transformation by synthesizing and releasing specific extracellular enzymes that hydrolyze the ester bonds in organic P complexes.

Step 2: Detailed Explanation:
The mineralization process is mediated by specific enzymes produced by soil bacteria and fungi under phosphorus-deficient conditions.
Phosphatases (specifically acid and alkaline phosphatases) are a broad group of enzymes that catalyze the hydrolysis of esters and anhydrides of phosphoric acid.
This enzyme cleaves the ester bonds, releasing free phosphate groups into the soil solution.
Phytases are a specialized subclass of phosphatases that specifically target phytic acid (myo-inositol 1,2,3,4,5,6-hexakisphosphate), which is the most abundant form of organic phosphorus in many soils.
Phytase sequentially cleaves the phosphate groups from the inositol ring, rendering the phosphorus soluble and plant-available.
In contrast, ATP sulfurylase is an enzyme involved in the assimilation of sulfur, specifically catalyzing the activation of sulfate.
Nitrogenase is the highly specialized enzyme complex responsible for biological nitrogen fixation, converting atmospheric dinitrogen (\( \text{N}_2 \)) into ammonia (\( \text{NH}_3 \)).
Therefore, ATP sulfurylase and nitrogenase do not play a role in organic phosphorus mineralization.
Thus, the enzymes directly responsible for cleaving organic P compounds are phosphatase and phytase.

Step 3: Final Answer:
The correct combination of enzymes is (B) and (C) only.