title: Carboxylated lysine is required for higher activities in Hydantoinases.
abstract: Hydantoinases are industrial enzymes with varying degree of activities on variable substrates to form different products. Although, few of the hydantoinase structures were known recently, the functional details and active site mechanism were not clearly understood yet. In a structure determination effort we reported that Bacillus sp. AR9 hydantoinase contains uncarboxylated lysine in the active site, whereas all the other hydantoinases have a carboxylated active site lysine. Here we describe the importance of carboxylated lysine for differential activities by making lysine mutations as well as carboxylating the lysine in a D-hydantoinase from Bacillus sp. AR9. The lysine to alanine and lysine to arginine mutations showed reduced activities whereas carboxylation of the lysine has enhanced the activity. Theoretical studies involving the calculation of electrostatic potentials for the hydroxide ion between the two metal ions present in the active site suggest that the presence of carboxylated lysine increases the nucleophilicity of the hydroxide.
authors.affiliation: Institute of Microbial Technology, Sector 39-A, Chandigarh 160 036 India.
authors.forename: Vijay
authors.initials: V
authors.lastname: Kumar
authors.forename: Neetu
authors.initials: N
authors.lastname: Saxena
authors.forename: Monika
authors.initials: M
authors.lastname: Sarma
authors.forename: K V
authors.initials: KV
authors.lastname: Radha Kishan
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001407:Bacillus / Q000201:enzymology; D008239:Lysine / Q000737:chemistry* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D013329:Structure-Activity Relationship
chemical_list: D000581:Amidohydrolases; C020047:dihydropyrimidinase; D008239:Lysine