It is not obvious if strB2 participates in streptomycin biosynthesis as an inosamine-phosphate amidinotransferase. Attempt to measure its activity have failed and the nucleophilic cysteine which is the key residue for amidine transfer is not conserved but replaced by a glycine residue. 1-amino-1-deoxy-scyllo-inositol 4-phosphate + L-arginine = 1-guanidino-1-deoxy-scyllo-inositol 4-phosphate + L-ornithine Antibiotic biosynthesis; streptomycin biosynthesis. Belongs to the amidinotransferase family.