- Which one of the following combinations of secondary metabolite biosynthetic pathway result in the biosynthesis of terpenes?
(1) Mevalonic acid and MEP pathways
(2) Malonic acid and MEP pathways
(3) Shikimik acid and Malonic acid pathway
(4) Shikimik acid and Mevalonic acid pathways
Correct answer: (1) Mevalonic acid and MEP pathways
Explanation:
-
Terpenes are synthesized via two distinct biosynthetic pathways in plants:
-
The Mevalonic acid (MVA) pathway, which operates in the cytosol, provides precursors mainly for sesquiterpenes, triterpenes, and sterols.
-
The 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway, also called the non-mevalonate pathway, located in plastids, supplies precursors for monoterpenes, diterpenes, and tetraterpenes.
-
-
Both pathways produce the universal five-carbon building blocks, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), which condense to form terpenes of various sizes.
-
Neither the malonic acid pathway nor the shikimic acid pathway contributes directly to terpene biosynthesis.
-
The shikimic acid pathway is involved in the biosynthesis of aromatic amino acids and phenolic compounds, while the malonic acid pathway mainly leads to fatty acids and polyketides.
Option-wise:
-
(1) Mevalonic acid and MEP pathways — Correct.
-
(2) Malonic acid and MEP pathways — Incorrect.
-
(3) Shikimic acid and Malonic acid pathways — Incorrect.
-
(4) Shikimic acid and Mevalonic acid pathways — Incorrect.
Terpene biosynthesis in plants occurs via the mevalonic acid pathway in the cytosol and the MEP pathway in plastids, both generating isopentenyl diphosphate and dimethylallyl diphosphate as precursors for diverse terpene compounds essential in plant growth and defense.
