Helicobacter pylori urease may exist in two forms: evidence from the kinetic studies.
Purified Helicobacter pylori urease displayed a sigmoid curve in the plot of velocity versus [S] at urea concentrations less than 0.1 mM. Under conditions where preservatives, glycerol, or polyethylene glycol (PEG), were added to the enzyme reaction, the substrate hydrolysis was consistent with Michaelis-Menten kinetics, with a Km of 0.21+/-0.06 mM and a Vmax of 1200+/-300 micromol min(-1) mg(-1). However, at saturating substrate concentrations, the kinetic parameters of H. pylori urease were unaffected by the presence of the preservatives, and enzyme catalysis conformed to Michaelis-Menten kinetics. The Hill coefficients of the enzyme-catalyzed urea hydrolysis in the presence and absence of PEG were 1 and 2, respectively. Based on these findings, we suggest that H. pylori urease may exist in aggregated and dissociated forms, each with intact function but differing kinetics that may be of importance in maximizing urea breakdown at varying urea concentrations in vivo.
Gang
Jin Gu
JG
Graduate School of Biotechnology, Korea University, Seoul, Korea.
Yun
Soon Kyu
SK
Hwang
Se Young
SY
D002384:Catalysis; D005990:Glycerol / Q000737:chemistry; D016481:Helicobacter Infections / Q000201:enzymology* / Q000382:microbiology; D016480:Helicobacter pylori / Q000201:enzymology*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D011092:Polyethylene Glycols / Q000737:chemistry; D014508:Urea / Q000737:chemistry / Q000378:metabolism; D014510:Urease / Q000737:chemistry / Q000378:metabolism
D011092:Polyethylene Glycols; D014508:Urea; D014510:Urease; D005990:Glycerol