N𝜀-Lysine acetylation participating in the regulation of protein function was first discovered by histones and is now detected on various proteins in all three domains of life. The acetyl group of the acetylated substrates can be erased by two types of deacetylase, Zn2+ dependent classic deacetylase and NAD+-dependent sirtuin. Besides proteins, small molecules like sugars, polyamines, or antibiotics can also be acetylated and deacetylated. Klebsiella pneumonia is an opportunistic pathogen frequently causing acute nosocomial infection. It is genetically closely related to Escherichia coli. However, only one sirtuin deacetylase was confirmed in the E. coli K12 strain, while K. pneumonia has, in addition, a class II classic deacetylase homolog, which is annotated as histone deacetylase-like amidohydrolase (HdaH). We confirmed its deacetylase activity with synthetic substrates but so far did not find any endogenous bacterial protein substrate. Further enzymatic and structural investigations imply it might be a native polyamine deacetylase. The aim of our research is a deeper understanding of the bacterial acetylation system, and providing knowledge for preventing and treating K. pneumonia infection.