Human platelet as an independent unit for sulfate conjugation
The human platelets possess a full complement of enzymes capable of synthesizing N-acetyldopamine (NADA) /sup 35/sulfate from ATP, Mg/sup + +/ and sodium /sup 35/sulfate. The pH optimum for this three-step overall sulfate conjugation (comprising of the ATP sulfurylase, APS kinase and phenolsulfotransferase reactions) is 8.6 and the reactions proceeded progressively for several hours. Both ATP and Mg/sup + +/ ions, above their respective optimal concentrations of 5 and 7 mM, inhibited the sulfate conjugation of NADA. The apparent Km values for NADA as determined by the phenolsulfotransferase (PST) and overall reactions were similar in magnitude being 2.6 and 4.8 ..mu..M, respectively, while that for sodium /sup 35/sulfate was 202 ..mu..M. A comparison of these two activities in 62 platelet preparations of normal subjects showed that the rate of the PST reaction was generally higher than the overall reaction even though the PST assay was carried out at suboptimal concentration of PAPS. There was a positive correlation (r=0.82) between the two sets of data, suggesting that the PST reaction probably has some control over the rate of overall sulfate conjugation.
- Research Organization:
- National Univ., Singapore
- OSTI ID:
- 5481533
- Journal Information:
- Life Sci.; (United States), Journal Name: Life Sci.; (United States) Vol. 42:11; ISSN LIFSA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
ATP
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BIOSYNTHESIS
BLOOD
BLOOD CELLS
BLOOD PLATELETS
BODY FLUIDS
CATIONS
CHARGED PARTICLES
DAYS LIVING RADIOISOTOPES
ENZYME ACTIVITY
ENZYMES
EVEN-ODD NUCLEI
IONS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MAGNESIUM COMPOUNDS
MAMMALS
MAN
MATERIALS
NUCLEI
NUCLEOTIDES
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PRIMATES
RADIOISOTOPES
REACTION KINETICS
SULFATES
SULFUR 35
SULFUR COMPOUNDS
SULFUR ISOTOPES
SYNTHESIS
TRACER TECHNIQUES
TRANSFERASES
VERTEBRATES