title: Single-molecular enzymatic elongation of hyaluronan polymers visualized by high-speed atomic force microscopy.
abstract: Using high-speed scanning atomic force microscopy, we directly observed single-molecular enzymatic elongation of hyaluronan polymer chains at intervals of 10 s on a mica or lipid bilayer surface, on which  Pasteurella multocida  hyaluronic acid synthase (pmHAS) was immobilized. The reaction was started by the addition of both UDP-glucuronic acid and UDP-N-acetylglucosamine monomers. The average catalytic elongation rate constant (k(cat)) was found to be 1.8 mer s(-1) from one active enzyme physically adsorbed on a mica surface. When pmHAS was immobilized by inserting its hydrophobic tail part into lipid bilayers, most of the enzymes retained their activity, and the k(cat) values were found to be in the range 1-10 mer s(-1) for 29 enzymes (average was k(cat) = 2-4 mer s(-1)). These k(cat) values were lowest level of k(cat) = 1-100 s(-1) obtained in bulk solution by radioisotope methods.
authors.affiliation: Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan. tmori@bio.titech.ac.jp
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Mori
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hirose
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hagiwara
authors.forename: Masanori
authors.initials: M
authors.lastname: Ohtsuka
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Kakuta
authors.forename: Koji
authors.initials: K
authors.lastname: Kimata
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Okahata
mesh_terms: D002384:Catalysis; D014453:Glucuronosyltransferase / Q000737:chemistry; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000737:chemistry*; D008051:Lipid Bilayers; D018625:Microscopy, Atomic Force / Q000379:methods*; D016979:Pasteurella multocida / Q000201:enzymology; D011108:Polymers / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D011108:Polymers; D006820:Hyaluronic Acid; D014453:Glucuronosyltransferase; D000076002:Hyaluronan Synthases