Mediates bacterial resistance to streptomycin (PubMed:3137862, PubMed:17609790). Adenylates streptomycin on the O-6 residue (PubMed:3137862, PubMed:15984036, PubMed:17609790). Adenylates streptidine on the O-6 residue (PubMed:17609790). Does not act on spectinomycin, neomycin-B or kanamycin (Ref.5, PubMed:15984036). Specific for ATP and GTP nucleotides incorporating a purine ring. No reaction with CTP or UTP (PubMed:15984036). ATP + streptomycin = 6-O-adenylylstreptomycin + diphosphate GTP + streptomycin = 6-O-guanylylstreptomycin + diphosphate ATP + streptidine = 6-O-adenylylstreptidine + diphosphate Optimum pH is 8.0. Optimum temperature is 35 degrees Celsius. Homodimer. Very slight reduction in streptomycin MIC. Could be used as a selectable marker in B.subtilis if strongly expressed, could be used as a selectable marker in E.coli (Ref.7). Streptidine restores the antibiotic effectiveness of streptomycin in bacterial strains in which they both are co-administered together with a simultaneous overexpression of this enzyme (PubMed:17609790). Although this enzyme can be purified from B.subtilis, the bacteria is sensitive to streptomycin in vivo.