The environment in which your protein is normally found should inform the conditions in which it is to be dissolved. For example, if it is a cytoplasmic protein, then it should be dissolved in an approximately neutral pH buffer with a reducing agent.

However, since you specified that it is a synthetic protein, I will assume that it was prepared by solid phase chemical synthesis and is therefore in a denatured state. It probably won't take on a folded tertiary structure when simply mixed with water, and there is no reason to expect an acidic solution to be helpful in this regard, unless the protein is normally found in an acidic environment (e.g. lysosomes).

As a synthetic protein, it may have no stable, folded conformation. Nevertheless, I think I would try to treat it as if it were a soluble protein produced in an aggregated, insoluble form and in need of denaturation and renaturation. This means dissolving it in a chaotrope such as 6M urea or guanidine HCl, then refolding it by one of the methods typically used for this purpose. There are kits available that supply various reagents to assist with refolding. You also need to consider whether it is necessary to form correct disulfide bonds. Successful refolding can be assessed by an activity assay.

The environment in which your protein is normally found should inform the conditions in which it is to be dissolved. For example, if it is a cytoplasmic protein, then it should be dissolved in an approximately neutral pH buffer with a reducing agent.

However, since you specified that it is a synthetic protein, I will assume that it was prepared by solid phase chemical synthesis and is therefore in a denatured state. It probably won't take on a folded tertiary structure when simply mixed with water, and there is no reason to expect an acidic solution to be helpful in this regard, unless the protein is normally found in an acidic environment (e.g. lysosomes).

As a synthetic protein, it may have no stable, folded conformation. Nevertheless, I think I would try to treat it as if it were a soluble protein produced in an aggregated, insoluble form and in need of denaturation and renaturation. This means dissolving it in a chaotrope such as 6M urea or guanidine HCl, then refolding it by one of the methods typically used for this purpose. There are kits available that supply various reagents to assist with refolding. You also need to consider whether it is necessary to form correct disulfide bonds. Successful refolding can be assessed by an activity assay.

I agree with the comments from Adam and would like to add a little more info. I would suggest to dissolve your protein in DMSO as a stock solution with a high protein concentration, then take aliquots and dissolve them in any buffer with physiological pH (suitable for your bioassay)  having different concentrations of reducing reagent like DTT (starting from 0.5 mM to 100 mM). Then, you need to get rid of DTT by centrifugation of your samples using Micro Bio-Spin 1 ml columns, and immediately after that test your samples in your bioactivity assay. The concentration of DTT that will give you the highest activity for your protein will help you to figure out your future strategy.   

I endorse Adam's advice, that in your case it would be appropriate to fully denature your protein in urea or guanidine hydrochloride buffer, followed by refolding your protein and validating the correctness of folding using an activity assay.  It will be a trial-and-error process, unfortunately, as there are no one-size-fits-all refolding techniques for proteins.

Here are a few things you should consider when optimizing the refolding conditions:

1. make sure that you start with fully reduced Cys residues by including fresh reducing agent in your denaturing buffer and incubating your protein for ~ 1 h at room temperature in this buffer, prior to refolding

2. Choose a pH of your refolding buffer that is +/- ~ 1 away from your protein's isoelectric point (pI).  A pH that is close to or at your pI will generally cause your protein to aggregate

3. optimize the ionic strength of your buffer by trying several salt concentrations

4. perform your refolding at low temperature either slowly, using dialysis or very quickly, using a rapid dilution technique.

Good luck!