Yes, it could. The addition of a specific carbohydrate structure definitely does an effect on the final physiologigal cell response. The effect of the changing the carbohydrate structure during the biosynthesis in the cells or bioreactor on the in vivo / in vitro  bioeffect can be reflected in many ways:

1) It can increase the half-life of the injected (in vivo) biological, because it can have more sialic acid content, and therefore, longer ability to circulate in the blood stream before to be absorbed (and exposed)  by receptors.

2) It can affect the affinity of the interaction of the biological to the receptor and the number of the receptor numbers occupied involved in the processes (because of the influence of the ligand on the receptor dissociation)  and that's would could lead to huge increase to the final cell response.

3) It can change the cell signal transduction pathways, and therefore change the very different final cell response.

4) It can make a big difference if the action applied at certain specific point of the time, like the action of some specific FSH glycoforms during the monthly periods in women.  

2) It can have direct effect on the activation of the receptor.   

Thank you so much Dr.Viktor Y Butnev for a great answer.That really helped. Now it is clear that glycan parts can really change the physiological response of any glycoprotein or pharmacodynamics of any glycoconjugate molecules.

But what do you think of the fact that glycan parts of natural drug molecules(like phenols) are being hydrolysed at the site of the receptor?. In the context of glycoproteins(like FSH) the glycan structures are the integral part of the protein. But in case of bio-active natural molecules like phenols these glycans are added to them via chemical synthesis in the laboratory to enhance either their bioavailability or their pharmacological action. Although many papers suggest that the glycoconjugate's pharmaclological effects are changed, and its stability&bioavailability have increased compared to their aglycan counter part, it is not still clear whether the glycan structure really stay attached to the drug molecule while it binds to its target. Many say that it will be hydrolysed and removed inside the blood stream. they suggest that these glycan structures just act as a vehicle to deliver the drug into the system(due to increased bioavailablilty when given orally). So what is your analysis on that? 

You need to consider the differences between glycosylation of a protein and glycosylation of a small molecule. Protein glycosylation in this context (therapeutic proteins) are often large glycan structures (>7 monosaccharides). Small molecule glycosylation are most of the time small additions (such as 1 or 2 monosaccharides) and the linkages are chemically depended, unlike protein glycosylation which are enzyme dependent.

I'm not that well-versed in small molecule glycosylation, but I recall examples of antimicrobial compounds getting increased bioactivity after glycosylation. It was due to the change in structure that anti-antimicrobial mechanism such as enzymatic breakdowns (beta-lactamase) or efflux pumps fail to bind to the glycosylated antimicrobial. That would definitely classify as changing in pharcological effects while remaining bound to the aglycon.

Thank you Dr.Edward Moh. Yes it makes sense. Glycosylation on smaller molecules indeed changes its pharmacological effects but the question is, will the glycan structure of these small molecules be intact while it binds to their targets? Sure some are bound to be hydrolysed either in the digestive system or inside the body. but is it really possible to synthesis glycoconjugates that are stable throughout the pharmacokinetic pathways?(any paper suggestion would be helpful).I believe that glycosylation is a great tool to fine tune the pharmacological activity of small molecules. Using glycans all I want to do is, to synthesis a series of glycoforms,each with different specificity towards different receptors, and finally screen for a particular glycoform that is potent in exerting a specific/desired cell physiology. Because most of these small molecules found in the nature are multifunctional with multitude of targets. So it would be great if we could increase their affinity towards specific receptors and thus enhancing a specific pharmacological activity. I am looking for experimental proofs for this.

Mr is fine, I'm still doing my PhD :p.  With regards to your research question, I think the straight answer is nobody knows. Every compound is different and you will not know until you try. Having said that, if you are trying to fine tune your target compounds' affinity towards a known receptor, using glycans might not be the best way to do it, in my opinion. Unless, if you have molecular simulations that suggest otherwise.

Glycans do not have specific receptors. While lectins can target a highly specific subset of glycans (LeX, SleX, high man, sialic acids etc), there is no 1 glycan, 1 receptor concept. On some proteins, the glycans can fine tune the interaction between the protein and its receptor (classic example will be IgG and FcgIIIR), while on some proteins, glycans are only for pharmacokinetic purposes (a classic would be erythropoietin). From my point of view, it goes do the relative size of the target - for a protein, a glycan change is insignificant in terms of physical size. For a small molecule, even adding a single monosaccharide is big (and the chemistry is not easy).  Such big changes might reduce your non specific target binding, but it could also give you new side targets. Having said that, if you have the facilities and resources to do that sort of high-throughput screening, go for it. 

Thank you dear Mr. Edward Moh. I agree with you totally. this idea came to me when I stumbled upon some studies where people were able to reduce off target effects and increased activity of specific signalling pathways by adding specific glycan structure to their small drug molecules.these glycoconjugates had same target specificity as their aglycons but their potency(with respect to specific pharmacological activity like anticancer etc) has increased greatly.But I am not sure if all their pharmacological activities(anti-cancer,anti-inflammatory etc) had equally increased or only specific activity they were interested in had increased because the studies I referred, they didn't look at the changes in their other pharmacological properties at the same time to demonstrate that.

My idea is not to synthesis specific glycoconjugates rationally to particularly target a specific receptor,which is almost impossible unless my target is a lectin. But what i am hoping to do is to synthesis a handful of glycoconjugates chemically with random glycan structures and then screen their activity to see whether any of them show increased activity towards any specific pathway, say increased anti-inflammatory activity rather than anticancer activity compared to their aglycon form. if I had enough experimental evidences to back this then sure I can try this. I have number of reasons to particularly choose glycans to do this for my work. So it would be nice if you could refer me to some papers where people have studied this. thank you.