Tony Byun

Degradation of N-acylhomoserine lactones, the bacterial quorum-sensing molecules, by acylase

Porcine kidney acylase I was shown to be able to deacylate N-acylhomoserine lactones, a family of chemicals employed by Gram-negative bacteria as quorum-sensing molecules for cell population density-dependent growth (such as biofilm formation). The enzyme transformed both N-butyryl-and N-octanoyl-L-homoserine lactones into L-homoserine. An optimal pH of 10 at 23 degrees C and an optimal temperature of 76 degrees C at pH 9 were found for the enzyme in hydrolyzing N-butyryl-homoserine lactone. At pH 9 and 23 degrees C, the enzymatic catalysis had a K(m) of 81+/-3 mM and a k(cat) of 127+/-2 nmol min(-1) per mg. The enzyme was also shown to be able to reduce the biofilm growth in an aquarium water sample. Potential physiological significance and medicinal/industrial applications of the N-acylhomoserine lactone-degrading activity of acylase are discussed.

Glycyl Aminopeptidase ( Sphingomonas )

Publisher Summary This chapter discusses the structural chemistry and the biological aspects of glycyl aminopeptidase. Sphingomonas capsulata glycyl aminopeptidase is a metallopeptidase specific for N-terminal glycine and alanine. The enzyme was isolated from the culture broth of S. capsulata IFO 12533. The aminopeptidase is a 66 kDa protein identified as a zinc metalloenzyme. The primary sequence of the enzyme contains a putative zinc-binding motif HEXXH. A homogeneous preparation of the aminopeptidase was obtained from the supernatant of S. capsulata IFO 12533 using conventional procedures that included anion-exchange and hydrophobic-interaction chromatography. Bacteria secrete a number of scavenger enzymes into the environment to obtain nutrients necessary for survival. This enzyme is a secreted protein and this would indicate that its primary function is to degrade extracellular proteins to allow efficient uptake of amino acids by the organism. Glycine and proline are among the most difficult residues for proteases to hydrolyze due to their unique structures. S. capsulata has evolved an aminopeptidase specific for glycine and a prolyl endopeptidase. It is suggested that S. capsulata possesses a number of different peptidases that would allow the degradation of proteins rich in both glycine and proline.