There are a few tools in the marketplace that will allow you to do this
successfully. I would suggest you take a look at the recent gartner analysis
and check out the vendors listed there from exposing mainframe transactions
as Web Services. I would also suggest looking for a solution that allows for
both publishing and consuming a web service. One of the vendors mentioned,
GT Software, will allow you to invoke a Web Service from the mainframe and
return the data to build what they call a Composite Mainframe Web Service.
Here is the link the the recent analysis report: