TY - JOUR
T1 - Human placental atp-diphosphohydrolase
T2 - Biochemical characterization, regulation and function
AU - Kettlun, A. M.
AU - Alvarez, A.
AU - Quintar, R.
AU - Valenzuela, M. A.
AU - Collados, L.
AU - Aranda, E.
AU - Banda, A.
AU - Chayet, L.
AU - C̀hiong, M.
AU - Mancilla, M.
AU - Traverso-Cori, A.
N1 - Funding Information:
Ack~owiedgeme~rs-This work was financed by Grants: FondecytN o. 90-1006D, TI 3345-923a3n d Universidadd e Chile PG 029-92.W e thank Sr Juan Espinoza from the Comision Chilena de Energia Nuclear who kindly carried out the irradiation-inactivatione xperiments.
PY - 1994/3
Y1 - 1994/3
N2 - 1. 1. Kinetic and physico-chemical studies on human placental microsomal fraction confirmed that the ATPase and ADPase activities detected in this fraction correspond to the enzyme ATP-diphosphohydrolase or apyrase (EC 3.6.1.5). These include substrate specificity, and coincident Mr and pI values of both ATPase-ADPase activities. 2. 2. This enzyme hydrolyses both the free unprotonated and cation-nucleotide complex, the catalytic efficiency for the latter being considerably higher. 3. 3. Microsomal apyrase is insensitive to ouabain and Ap5A. The highly purified enzyme was only inhibited by o-vanadate, DBS and slightly by DCCD. 4. 4. Apyrase seems to be a glycoprotein from its interaction with Concanavalin-A. 5. 5. Preliminary studies on the essential amino acid residues suggest the participation of Arg, Lys and His residues, and discard the requirement of -SH, COO-, -OH, and probably also Tyr and Trp. 6. 6. Two kinetic modulatory proteins of apyrase were detected in placental tissue. An activating protein was found in the soluble fraction and an inhibitory protein was loosely bound to the membranes. 7. 7. The proposed in vivo function for apyrase is related to the inhibition of platelet aggregation due to its ADPase activity, which is supported by the direct effect on washed platelets and by its plasma membrane localization.
AB - 1. 1. Kinetic and physico-chemical studies on human placental microsomal fraction confirmed that the ATPase and ADPase activities detected in this fraction correspond to the enzyme ATP-diphosphohydrolase or apyrase (EC 3.6.1.5). These include substrate specificity, and coincident Mr and pI values of both ATPase-ADPase activities. 2. 2. This enzyme hydrolyses both the free unprotonated and cation-nucleotide complex, the catalytic efficiency for the latter being considerably higher. 3. 3. Microsomal apyrase is insensitive to ouabain and Ap5A. The highly purified enzyme was only inhibited by o-vanadate, DBS and slightly by DCCD. 4. 4. Apyrase seems to be a glycoprotein from its interaction with Concanavalin-A. 5. 5. Preliminary studies on the essential amino acid residues suggest the participation of Arg, Lys and His residues, and discard the requirement of -SH, COO-, -OH, and probably also Tyr and Trp. 6. 6. Two kinetic modulatory proteins of apyrase were detected in placental tissue. An activating protein was found in the soluble fraction and an inhibitory protein was loosely bound to the membranes. 7. 7. The proposed in vivo function for apyrase is related to the inhibition of platelet aggregation due to its ADPase activity, which is supported by the direct effect on washed platelets and by its plasma membrane localization.
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U2 - 10.1016/0020-711X(94)90065-5
DO - 10.1016/0020-711X(94)90065-5
M3 - Article
C2 - 8187939
AN - SCOPUS:0028175708
SN - 0020-711X
VL - 26
SP - 437
EP - 448
JO - International Journal of Biochemistry
JF - International Journal of Biochemistry
IS - 3
ER -