While it makes no sense whatsoever, I'm getting some good hits in HHPred to "Caudovirus prohead serine protease" (98% probability, ~95% coverage; see attachment) for GC phage Rasputia gp130 (in phagesdb and Phamerator gp130. That's the same as "capsid maturation protease," no? Note that this is an orpham, and we've already got a capsid maturation protease (where it should be!)

I'd like to call this simply "peptidase" for now, but I'd love a second opinion on this. It's such a good match in HHPred!