Question

The enzyme checked for confirmation of Bifidobacterium is

• A. Fructose-6-phosphatase
• B. Fructose-6-ketolase
• C. Fructose-6-phosphate phosphoketolase
• D. Fructose-6-phosphate dehydrogenase

Hint:

Diagnostic Probiotic Enzymes:
Bifidobacterium Confirmation = FRUCTOSE-6-PHOSPHATE PHOSPHOKETOLASE (F6PPK 'Bifid shunt').
Ferments Glucose $\rightarrow$ Acetate : Lactate (3 : 2 molar ratio).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Probiotic taxonomy and diagnostic enzymology: Genus Bifidobacterium is uniquely identified by the presence of Fructose-6-Phosphate Phosphoketolase (F6PPK), the key pathway-defining enzyme of the 'Bifid shunt'.
Key Formula or Approach:
\[ \text{Fructose-6-P} + \text{P}_i \xrightarrow{\mathbf{F6PPK \text{ (Fructose-6-Phosphate Phosphoketolase)}}} \text{Erythrose-4-P} + \text{Acetyl-Phosphate} \]

Step 2: Detailed Explanation:
In probiotic microbiology and taxonomy of the genus Bifidobacterium:
- Bifidobacterium species (e.g., B. bifidum, B. animalis subsp. lactis, B. longum) do not ferment hexoses via standard glycolysis (EMP) or the 6-phosphogluconate pathway.
- Instead, they exclusively utilize a unique metabolic pathway termed the 'Bifid Shunt' (Fructose-6-Phosphate Shunt) that converts 2 moles of glucose into 3 moles of acetate and 2 moles of L-lactate.
- The key signature enzyme that is strictly unique and diagnostic for the genus {Bifidobacterium is Fructose-6-Phosphate Phosphoketolase (F6PPK) (C). The standard diagnostic enzymatic laboratory assay (Scardovi test) for confirming an isolate as a Bifidobacterium is testing for active F6PPK cellular activity.

Step 3: Final Answer:
Therefore, the enzyme checked for confirmation is Fructose-6-phosphate phosphoketolase, matching option (C).