TABLE 10.

AAC(6′)Ib-cr variants with demonstrated quinolone-acetylating activity^a

GenBank accession no.	IDb	Size (no. of amino acids)	Amino acid positionc										Quinolone(s)d	Reference
WP_001749987	cr5	199	M1	S2	N3	A4	K5	N20	R102	L117	Y179	D198	CIP, NOR, TSX	170
EUM72348		202	I	Q	H	F	Q				D	V	CIP	406
—e		?	?	?	?	?	?				G	?	CIP	406
EUM72320		199							W				CIP, GMX, ZBX	406
WP_015059932	cr4	225	T	P	G	N	D	T					CIP, NOR	409

^aCIP, ciprofloxacin; GMX, gemifloxacin; NOR, norfloxacin; TSX, tosufloxacin; ZBX, zabofloxacin. Amino acids considered relevant for the acetylation of quinolones are highlighted in boldface type. Note that possible enhanced or diminished activity as well as expanded or contracted substrate profile alterations might be related to nonhighlighted amino acid differences. The absence of a specific quinolone does not preclude the inability of the enzyme to inactive it.

^bIn the description present in GenBank, note that the first described AAC(6′)Ib-cr enzyme (170) is numbered “cr5.”

^cFollowing the numeration provided by Robicsek et al. (170), note that the different sizes of acetylases may lead to different numeric positions in any variant. For instance, the reported amino acid substitution “N₂₀T” under GenBank accession number WP_015059932 is located in the equivalent position 46. When longer, amino acid positions prior to M₁ under GenBank accession number WP_001749987 have not been analyzed.

^dQuinolones which might be acetylated.

^eNo GenBank accession number is provided in the article by Kim et al. (406), and after a search in GenBank using the sequence under accession number WP_001749987 and introducing a glycine in position 179, no concordant enzyme was found among the first 100 results.