Question

Bacterial cells generally lack the glycosyltransferase enzymes required to attach oligosaccharides (sugar oligomers) to proteins. How does the absence of these enzymes limit the use of bacterial expression systems in producing human proteins?

Answer 1

Bacteria are prokaryotic organisms that exhibit a simple structure.
They do not contain a nucleus and membrane-bound organelles.

There are several problems associated with the expression of eukaryotic proteins in a prokaryotic system.
1. Prokaryotes do not possess splicing machinery. So, eukaryotic genomic DNA should not be used for cloning. Only cDNA should be used for cloning the gene.
2. Prokaryotes do not possess ER and Golgi complex that are involved in post-translational modifications. These modifications include proteolytic cleavage, glycosylation, phosphorylation, etc. These modifications are essential for the proper folding, localization, stability, and activity of eukaryotic proteins. Since prokaryotes do not have these systems, it is difficult to express functional eukaryotic genes in prokaryotic hosts.

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