+1 on what Yooper said. Yeast make the wine. Enzymes are usually referred to in mashing for starch to sugar convergence. I think if it's considered pasteurized then adding the yeast shouldn't be an issue.
Natural grape soda sounds awesome. I'd do it!
Camp Brew Co.
Primary: IryePA 5.0
2ndary aging: None
On Tap: IryePA 4.0, AmberHop ale-session version
Bottled: Bourbon Bbl Po' Boy Stout, Bourbon Oak Brolic Strong ale