Plant Growth Regulators & Plant Development

• Carbonic anhydrase $\rightarrow$ (II) $\text{Zn}^{2+}$: Contains an essential zinc ion coordinated by three histidine residues that activates water for hydration of $\text{CO}_2$ to $\text{HCO}_3^-$.
• Hexokinase $\rightarrow$ (IV) $\text{Mg}^{2+}$: Requires magnesium ($ ext{Mg}^{2+}$) as a cofactor to chelate the negative charges of ATP, forming the true active substrate $\text{MgATP}^{2-}$.
• Nitrate Reductase $\rightarrow$ (I) Mo: Contains a molybdenum pterin cofactor (Moco) essential for transferring electrons to reduce nitrate ($\text{NO}_3^-$) to nitrite ($\text{NO}_2^-$).
• Urease $\rightarrow$ (III) $\text{Ni}^{2+}$: A nickel-dependent metalloenzyme that hydrolyzes urea into ammonia and carbon dioxide.

Correct option: (4) (A) - (II), (B) - (IV), (C) - (1), (DB) - (Ill)

• Clostridium botulinum $

ightarrow$ (IV) Neurotoxin: Produces botulinum toxin (BoNT), a zinc-dependent metalloprotease that cleaves SNARE proteins to block acetylcholine release, causing flaccid paralysis.

• Staphylococcus aureus $

ightarrow$ (III) Enterotoxin: Secretes heat-stable staphylococcal enterotoxins (superantigens) that induce acute emesis and gastroenteritis.

• Aspergillus parasiticus $

ightarrow$ (II) Aflatoxin: Produces difuranocoumarin mycotoxins (Aflatoxins B1, B2, G1, G2), which are potent hepatocarcinogens.

• Aspergillus ostianus $

ightarrow$ (V) Ochratoxin A: Synthesizes the nephrotoxic pentaketide mycotoxin ochratoxin A.

• Penicillium expansum $

ightarrow$ (I) Patulin: Produces the polyketide mycotoxin patulin, commonly contaminating rotting deciduous pome fruits (apples).

Correct option: (3) (A) — (IV), (B) - (III), (C) - (I), (D) = (VY), (E) = (1)