Regulation cross-check: an intermediate that inhibits fructose-1,6-bisphosphatase would primarily inhibit which pathway?

Introduction / Context:
Control points in metabolism are often targeted by feedback signals. Fructose-1,6-bisphosphatase (F-1,6-BPase) is a key gluconeogenic enzyme that reverses the phosphofructokinase-1 step of glycolysis. Understanding which pathway is affected by its inhibition highlights reciprocal regulation between glycolysis and gluconeogenesis.

Given Data / Assumptions:

• F-1,6-BPase converts fructose-1,6-bisphosphate to fructose-6-phosphate.
• It is a rate-controlling step unique to gluconeogenesis (not present in glycolysis).
• Allosteric regulators (e.g., AMP, fructose-2,6-bisphosphate) inhibit F-1,6-BPase.

Concept / Approach:
If an intermediate or regulator inhibits F-1,6-BPase, the glucose-synthesizing pathway is suppressed. In many tissues, increased fructose-2,6-bisphosphate inhibits F-1,6-BPase while stimulating phosphofructokinase-1, thereby favoring glycolysis over gluconeogenesis.

Step-by-Step Solution:
1) Identify the enzyme's pathway: F-1,6-BPase is a gluconeogenic bypass enzyme.2) Inhibition reduces conversion of F-1,6-BP to F-6-P.3) This slows glucose production from precursors, i.e., inhibits gluconeogenesis.

Verification / Alternative check:
Physiological conditions that raise AMP or fructose-2,6-bisphosphate (e.g., fed state, high insulin) suppress hepatic gluconeogenesis, consistent with F-1,6-BPase inhibition.

Why Other Options Are Wrong:
Glycolysis is enhanced, not inhibited, when F-1,6-BPase is suppressed; “pyrolysis” is a non-biological thermal decomposition process; “none” contradicts known regulation; pentose phosphate pathway is controlled elsewhere (e.g., glucose-6-phosphate dehydrogenase).

Common Pitfalls:
Assuming every fructose phosphate enzyme belongs to glycolysis; F-1,6-BPase is exclusive to gluconeogenesis.

Final Answer:
Gluconeogenesis