Glucosyl Transferase: From Genesine to the Macromolecule
Krisman, C.R., Tolmasky, D.S., Lerner, L.R., Curá, J.A.
Instituto de Investigaciones Bioquímicas, "Luis F. Leloir", Fundación Campomar; CONICET; UBA. Av. Patricias Argentinas 435, (1405) Capital Federal, Argentina.
It is well established as we have postulated and demonstrated for the first time that in the "de novo" biogenesis of glycogen a protein GENESINE (from genesis: origin), the naked autoglucosylating protein is involved in the initial steps. In most of the glycogen forming tissues it is possible to find free "Genesine" as well as covalently associated with glycosyl-oligosaccharides named "glycogenin".
Selecting appropriate incubation conditions the naked autoglucosylating "Genesine" exhibits two transglucosylating activities involved in the first steps of the growing process. Mn++ stimulates the first trasnfer of glucose to "genesine" but further growth of the glucooligosaccharide chain linked to that protein is inhibited by Mn++ or Mn++ +Glc6P. Rat, brain, heart and liver were used for that studies. The results is the appearance of a 14C-radiolabelled protein band of 42 kDa and a faint one of 38 kDa. However, Mn++ is not an absolute requirement as in its absence "genesine" became glucosylated and a band of 60 kDa appeared. Finally in the growing process, the (14C) glucosylated protein bands were incorporated into the glycogen molecule. We were able to go back to "genesine" under controlled degrading conditions with -amylase.
Independently from the amount or type of starch polysaccharide synthesized by different corn mutants (amylose extender, waxy, shrunken, sugary, flint) and commercial wheat, the UDPGlc autoglycosylating activity "Genesine" involved in starch biogenesis was also detected 14C-glucosylated protein bands of 39,6 kDa and 38 kDa were obtained. Similarly to the above mentioned mammalian tissues. Mn++ is not an absolute requirement for the growing process of starch biogenesis and more than one enzymatic activity is also involved in this process.
This paper is specially dedicated to the memory of an excellent scientist and honorable person, Dr. Jerome F. Fredrick.
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Tuesday, April 7 |
03:20 pm |