Formation of enzyme-bound and medium pyrophosphate and the molecular basis of the oxygen exchange reaction of yeast inorganic pyrophosphatase

Journal Article · Mon Jan 01 00:00:00 EST 1979 · J. Biol. Chem.; (United States)

OSTI ID:5437791

Janson, C A; Degani, C; Boyer, P D

Yeast inorganic pyrophosphatase, with 10 mM /sup 32/P/sub i/ and 10 mM Mg/sup 2 +/ present at pH 7.3 to 7.6, rapidly forms enzyme-bound pyrophosphate equivalent to about 5% of the total catalytic sites on the two enzyme subunits. The enzyme thus appears to bind PP/sub i/ so as to favor thermodynamically its formation from P/sub i/. The enzyme catalyzes a measurable equilibrium formation of free PP/sub i/ at a much slower rate. Under similar conditions, the enzymes catalyzes a rapid exchange of oxygen atoms between P/sub i/ and water with the relative activation by metals being Mg/sup 2 +/ > Zn/sup 2 +/ > Co/sup 2 +/ > Mn/sup 2 +/. Millisecond mixing and quenching experiments demonstrate that the rate of formation and cleavage of the enzyme-bound PP/sub i/ is rapid enough to explain most or all of the oxygen exchange reaction.

• Research Organization: Univ. of California, Los Angeles, CA (United States)
• OSTI ID: 5437791
• Journal Information: J. Biol. Chem.; (United States), Vol. 254:10
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
BIOCHEMICAL OXYGEN DEMAND
BIOCHEMICAL REACTION KINETICS
PYROPHOSPHATES
BIOCHEMISTRY
CATALYSIS
ENZYMES
PHOSPHORYLATION
THERMODYNAMICS
YEASTS
CHEMICAL REACTIONS
CHEMISTRY
FUNGI
KINETICS
MICROORGANISMS
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
PLANTS
REACTION KINETICS
550200* - Biochemistry
550700 - Microbiology