4 research outputs found
Sialylation of lactosyl lipids in membrane microdomains by T.cruzi trans-sialidase
SolubleT. cruzi trans-sialidase transformed a synthetic lactosyl glycolipid in microdomains more slowly than the same substrate dispersed across the bilayer surface, producing phospholipid vesicles with a Neu5Ac(α2-3)Gal(ÎČ1-4)Glc âglycocalyxâ.</p
Accelerated Enzymatic Galactosylation of <i>N</i>âAcetylglucosaminolipids in Lipid Microdomains
A fluoro-tagged <i>N</i>-acetylglucosamine-capped glycolipid
that can form lipid microdomains in fluid phospholipid bilayers has
been shown to be enzymatically galactosylated by bovine ÎČÂ(1,4)-galactosyltransferase.
MALDI MS, HPLC, and LCâMS revealed that the rate of enzymatic
transformation was significantly enhanced by lipid clustering; at
a 1% mol/mol loading, clustered glycolipids were galactosylated 9-fold
faster than glycolipids dispersed across the bilayer surface. The
transformation of the GlcNAc âglycocalyxâ into a GalÂ(ÎČ1â4)ÂGlcNAc
âglycocalyxâ relabeled these vesicles, making them susceptible
to agglutination by <i>Erythrina cristagalli</i> lectin
(ECL). The kinetic parameters for this transformation revealed a lower
apparent <i>K</i><sub>m</sub> when the substrate lipids
were clustered, which is attributed to multivalent binding to an extended
substrate cleft around the active site. These observations may have
important implications where soluble enzymes act on substrates embedded
within cellular lipid rafts