β-lactamase is a class of bacterial enzymes that degrade β-lactam antibiotics, such as penicillins and cephalosporins. These enzymes are categorized into four major classes based on their function and sequence: A, B, C, and D. β-lactamase is primarily located in the bacterial cytoplasm, where it hydrolyzes the β-lactam ring to disrupt the structure of antibiotics, thereby resisting their bactericidal effects. Gene expression of β-lactamase is influenced by various regulatory mechanisms, including inducible and constitutive expressions. Mutations often enhance resistance to novel β-lactam antibiotics.