Vicia villosa B4 lectin inhibits nucleotide pyrophosphatase activity toward UDP-GalNAc specifically.
Plant seed lectins play a defense role against plant-eating animals. Here, GalNAc-specific Vicia villosa B4 lectin was found to inhibit hydrolysis of UDP-GalNAc by animal nucleotide pyrophosphatases, which are suggested to regulate local levels of nucleotide sugars in cells. Inhibition was marked at low concentrations of UDP-GalNAc, and was reversed largely by the addition of GalNAc to the reaction mixture. In contrast, lectin inhibited enzymatic hydrolysis of other nucleotide sugars, such as UDP-Gal and UDP-GlcNAc, only to a small extent, and GalNAc did not affect such an inhibition. The binding constant of the lectin for UDP-GalNAc was as high as 2.8 x 10(5) M-1 at 4 degrees C, whereas that for GalNAcalpha-1-phosphate was 1.3 x 10(5) M-1. These findings indicate that lectin inhibition of pyrophosphatase activity toward low concentrations of UDP-GalNAc arises mainly from competition between lectin and enzyme molecules for UDP-GalNAc. This type of inhibition was also observed to a lesser extent with GalNAc-specific Wistaria floribunda lectin, but not apparently with GalNAc-specific soybean or Dolichos biflorus lectin. Thus, V. villosa B4 lectin shows unique binding specificity for UDP-GalNAc and has the capacity to modulate UDP-GalNAc metabolism in animal cells.
Takeya
A
A
Department of Legal Medicine, St. Marianna University School of Medicine, Kanagawa, Japan. a2takeya@marianna-u.ac.jp
Hosomi
O
O
Kogure
T
T
D000818:Animals; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007887:Fabaceae; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D037102:Lectins / Q000494:pharmacology*; D037121:Plant Lectins; D010946:Plants, Medicinal; D011755:Pyrophosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013379:Substrate Specificity; D014536:Uridine Diphosphate N-Acetylgalactosamine / Q000378:metabolism
D004791:Enzyme Inhibitors; D037102:Lectins; D037121:Plant Lectins; C042242:Vicia lectins; D014536:Uridine Diphosphate N-Acetylgalactosamine; D011755:Pyrophosphatases; C021899:nucleotide pyrophosphatase