Direct measurement of newly synthesized ATP dissociation kinetics in sarcoplasmic reticulum ATPase
Incubation of SR vesicles with CaS and (TSP)acetylphosphate, yields steady state levels of (TSP)phosphorylated enzyme (ATPase) intermediate and high concentrations of CaS in the lumen of the vesicles. At this time, addition of ADP (and EGTA to lower the CaS concentration in the medium outside the vesicles) results in single cycle formation of (el-TSP)ATP by transfer of (TSP)phosphate from the enzyme intermediate to ADP. The phosphoenzyme decay and ATP formation exhibit a fast component within the first 20 msec following addition of ADP, and a slower component reaching an asymptote in approximately 100 msec. They have now measured by a rapid filtration method the fraction of newly synthesized ATP which is bound to the enzyme, as opposed to the fraction dissociated into the medium. They find that nearly all the ATP formed during the initial burst is still bound to the enzyme within the initial 20 msec of reaction. Dissociation of newly synthesized ATP occurs then with approximately 13 sec rate constant, permitting reequilibration of the system and further formation of ATP. The rate limiting effect of ATP dissociation and other partial reactions on the slow component of single cycle ATP synthesis is evaluated by appropriate kinetic simulations.
- Research Organization:
- Univ. of Maryland School of Medicine, Baltimore
- OSTI ID:
- 6156432
- Report Number(s):
- CONF-870644-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 46:6; ISSN FEPRA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
ADP
ATP
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOSYNTHESIS
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
ENZYMES
ESTERS
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANOIDS
PHOSPHOHYDROLASES
PHOSPHORIC ACID ESTERS
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
RADIOISOTOPES
REACTION KINETICS
SARCOPLASMIC RETICULUM
SYNTHESIS
TRACER TECHNIQUES