Catalysis of the reaction: acetyl-CoA + gentamicin C(1a) = N(2')-acetylgentamicin C(1a) + CoA + H+. This is acetylation of the 2'-amino group of the 6-deoxy-6-aminoglucose ring.
The process in which B cells acquire the specialized features of B-1a B cells. B-1a B cells are B-1 cells that express CD5 and arise from fetal liver precursors.