title: Mimosa pudica apyrase requires polysaccharide and Ca2+ for the activity.
abstract: Mimosa pudica Linn leaves with pulvini contain unique isoforms (I and II) of Apyrase enzyme (EC 3.6.1.5). The activity of isoform I depends on divalent cation Mn2+. This isoform is associated noncovalently with the polysaccharide, containing mainly of galactose and arabinose sugars. The apparent molecular mass of these 2 isoforms are 36 and 34 Kd respectively. The association of the polysaccharide with the isoform I has been found to be Ca2+ dependent which is endogenously present in this isoform. Removal of Ca2+ and polysaccharide from the enzyme (isoform I) leads to an inactivation. The enzyme activity can be restored when both Ca2+ and endogenous polysaccharide fraction were added at an optimal molar ratio of Ca2+:protein of 7:1. The endogenous polysaccharide can be replaced by the standard arabinogalactan. No other sugar or polysaccharide except the arabinogalactan can restore the apyrase activity. Calcium mediates a conformational change in the protein which helps in association of polysaccharide as evidenced from fluorometric and far UV-CD studies to restore the enzymic activity. Neither any interaction of the polysaccharide with the protein is detected in absence of Ca2+ nor the enzyme activity could be recovered under such condition.
authors.affiliation: Department of Biochemistry, Bose Institute, Calcutta, India.
authors.forename: R
authors.initials: R
authors.lastname: Ghosh
authors.forename: P C
authors.initials: PC
authors.lastname: Sen
authors.forename: S
authors.initials: S
authors.lastname: Biswas
mesh_terms: D000681:Amylases / Q000494:pharmacology; D001051:Apoenzymes / Q000378:metabolism; D001081:Apyrase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D001089:Arabinose / Q000032:analysis; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002614:Chelating Agents / Q000494:pharmacology; D002942:Circular Dichroism; D005685:Galactans / Q000378:metabolism / Q000494:pharmacology; D005690:Galactose / Q000032:analysis; D019791:Guanidine / Q000494:pharmacology; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology*; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D014268:Trifluoperazine / Q000494:pharmacology; D014364:Tryptophan / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology; D043325:Xylan Endo-1,3-beta-Xylosidase; D014995:Xylosidases / Q000494:pharmacology
chemical_list: D001051:Apoenzymes; D002121:Calcium Channel Blockers; D002614:Chelating Agents; D005685:Galactans; D007527:Isoenzymes; D011134:Polysaccharides; D014268:Trifluoperazine; D014364:Tryptophan; D001089:Arabinose; D014700:Verapamil; D000681:Amylases; D014995:Xylosidases; D043325:Xylan Endo-1,3-beta-Xylosidase; D001081:Apyrase; D000252:Calcium-Transporting ATPases; D019791:Guanidine; C005653:arabinogalactan; D002118:Calcium; D005690:Galactose