Siris Capital Group, a private equity firm, agreed to acquire American Stock Transfer & Trust, a professional services firm, from Pacific Equity Partners, an Australasian private equity investment firm, for $595m. The deal would value AST at 12.6-times trailing earnings, on an EBITDA to enterprise value basis. Siris Capital is expected to combine AST with UK-listed Equiniti Group, which has also signed a deal to acquire later this month.