How should a product manager support business development?

It depends on what the company means by "business development".  Generally speaking, a product manager should be available to meet with and discuss business opportunities with prospective clients and partners, with an angle on obtaining from them information that relates to undiscovered problems that the company can solve.What a product manager should not do in a business development context is an order taker for "that one feature that will totally close this deal."  There is rarely, if ever, reason to shift your priorities for one deal.