ISSN:
1573-4919
Keywords:
Mimosa pudica
;
apyrase
;
arabinogalactan
;
calcium
;
circular dichroism
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1006855627784
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