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Keywords:

  • carbohydrate synthesis;
  • cluster effect;
  • enzyme catalysis;
  • glycolipid membrane;
  • glycosyltransferase;
  • immobilization;
  • maltose-binding protein;
  • surface plasmon resonance

Abstract

β(1[RIGHTWARDS ARROW]4) Galactosyltransferase expressed as a fusion protein with maltose binding protein (MBP-GalT) was displayed specifically on a Langmuir–Blodgett (LB) membrane prepared by photopolymerization of maltotriose-carrying glycolipid (1) with 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (2). The catalytic activity of MBP-GalT on the LB film was directly monitored by the surface plasmon resonance (SPR) method using a GlcNAc-carrying water-soluble polymer (3) as an acceptor substrate. Highly sensitive sigmoidal-type signals were obtained upon the addition of the acceptor substrate in the presence of the donor substrate, UDP-galactose (UDP-Gal), while the binding of 3 was not detected in the absence of UDP-Gal. The intensities of the signals were dependent on the amount of immobilized MBP-GalT on the LB film, which was estimated from the images obtained by atomic force microscope (AFM).