Several Factors Regulate Glycosylation of Glycoproteins

Glycosyltransferase Family Donor Substrate

Fucosyltransferase GDP-Fucose

Sialyltransferase CMP-Neuraminic acid

Galactosyltransferase UDP-Galactose

N-Acetyl glucosaminyl transferase UDP- N-Acetyl glucosamin

N-Acetyl galactosaminyl transferase UDP- N-Acetyl galactosamin

Mannosyltransferase GDP-Mannose

Glucosyltransferase UDP-Glucose

Suitable acceptor sites in proteins.

The tissue level of Dol-P.

The activity of the oligosaccharide:protein transferase.

Different cells give different enzymes.

Certain glycosyltransferases act only on the oligosaccaride chain if it has already been acted

upon by another previous enzyme.

EX: action of GlcNAc is important for Golgi alpha-mannosaidase.

During which some genes are turned on & others are turned off.

Each enzyme has its own destination for insertion.

Ex:HMG.CoA reductase ER membrane it may never encounter Golgi-located processing enzyme.

Differences in proteins conformation may hinder access of proccessing

enzymes.

•The same cells(ex:fibroblast) of different species exhibit

different patterns of processing enzymes.

•Species variation is an important factor which is used for production of Glycoproteins

of Therapeutic use by Recombinant DNA tech.

EX:synthesizedErythropoietin (EPO)

1. Synthesized EPO is administered to patients with chronic anemia in order to stimulate Erythropoiesis.

2. The half-life of EPO in plasma is influenced by the nature of its glycosylation pattern.

3. Some species give patterns with short HL, others give them with normal HL.

Different & ubnormalglycosyl

transferases

More branching oligosacc.

chains

Loss of Adhesion

1• By lysosomal acid hydrolases.

2• They are Exo-enzymes.

3

• If anyone is missing ,degradation can’t

complete>>>>Leading to diseases!