**Question:** BANA test measures activity of

A. Carboxypeptidase
B. Proline amidohydrolase
C. N-acetylneuraminidase
D. N-acetylglucosaminidase

**Correct Answer:** D. N-acetylglucosaminidase

**Core Concept:** The BANA test (Benzoyl-L-arginine-p-nitroanilide) is used to measure the activity of enzymes involved in the degradation of bacterial cell walls, particularly the hydrolysis of bacterial endopeptidases.

**Why the Correct Answer is Right:** The correct answer, N-acetylglucosaminidase, is an enzyme responsible for breaking down N-acetylglucosamine, which is an essential component of bacterial cell walls. In the BANA test, this enzyme hydrolyzes benzoyl-L-arginine-p-nitroanilide (BANA) substrate, releasing p-nitroaniline which is measured spectrophotometrically. This test is used as a diagnostic tool to detect certain bacteria, such as Staphylococcus aureus, which produces endopeptidases.

**Why Each Wrong Option is Incorrect:**

A. Carboxypeptidase: This is an enzyme responsible for cleaving carboxyl terminal amino acids from proteins and peptides. It is not involved in the degradation of bacterial cell walls.

B. Proline amidohydrolase: This enzyme is involved in the degradation of peptidoglycan, but not specifically the BANA test.

C. N-acetylneuraminidase: This enzyme is involved in the degradation of sialic acid, another component of bacterial cell walls, but not specifically in the BANA test.

**Clinical Pearl:** The BANA test is a valuable diagnostic tool in identifying certain pathogenic bacteria, particularly Staphylococcus aureus, which is particularly useful in clinical microbiology labs. Understanding the role of different enzymes in bacterial cell wall degradation is essential for accurate interpretation of test results and appropriate antimicrobial therapy.