Isotopic probes of the argininosuccinate lyase reaction. Academic Article

abstract

• The mechanism of the argininosuccinate lyase reaction has been probed by the measurement of the effects of isotopic substitution at the reaction centers. A primary deuterium isotope effect of 1.0 on both V and V/K is obtained with (2S,3R)-argininosuccinate-3-d, while a primary 15N isotope effect on V/K of 0.9964 +/- 0.0003 is observed. The 15N isotope effect on the equilibrium constant is 1.018 +/- 0.001. The proton that is abstracted from C-3 of argininosuccinate is unable to exchange with the solvent from the enzyme-intermediate complex but is rapidly exchanged with solvent from the enzyme-fumarate-arginine complex. A deuterium solvent isotope effect of 2.0 is observed on the Vmax of the forward reaction. These and other data have been interpreted to suggest that argininosuccinate lyase catalyzes the cleavage of argininosuccinate via a carbanion intermediate. The proton abstraction step is not rate limiting, but the inverse 15N primary isotope effect and the solvent deuterium isotope effect suggest that protonation of the guanidino group and carbon-nitrogen bond cleavage of argininosuccinate are kinetically significant.

authors

• Raushel, Frank

published proceedings

• Biochemistry

author list (cited authors)

• Kim, S. C., & Raushel, F. M.

citation count

• 17

complete list of authors

• Kim, SC||Raushel, FM

publication date

• August 1986

publisher

• American Chemical Society (ACS)  Publisher

published in

• Biochemistry  Journal

keywords

• Animals
• Argininosuccinate Lyase
• Argininosuccinic Acid
• Cattle
• Isotope Labeling
• Kinetics
• Liver
• Lyases
• Nitrogen Isotopes
• Protein Binding

PubMed Central ID

• 3768310

Digital Object Identifier (DOI)

• 10.1021/bi00365a004

start page

• 4744

end page

• 4749

volume

• 25

issue

• 17

URL

• http://dx.doi.org/10.1021/bi00365a004