According to the Ambler structural classification of beta-lactamases, which class consists of zinc-dependent enzymes whose activity is abolished by chelating agents such as EDTA?

• A Class A
• B Class D
• C Class C
• D Class B ✓

Explanation

Ambler class D enzymes are metallo-beta-lactamases such as NDM, VIM and IMP. They require divalent zinc ions at the active site for catalysis, so EDTA chelation abolishes their activity, a property exploited in the combined disk test and in the EDTA-modified carbapenem inactivation method. Class A (KPC), class C (AmpC) and class B (OXA) enzymes are serine hydrolases with an active-site serine residue and are unaffected by EDTA.

Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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