21 CFR § 173.170 - Aminoglycoside 3′-phosphotransferase II.
---
identifier: "/us/cfr/t21/s173.170"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 173.170 - Aminoglycoside 3′-phosphotransferase II."
title_number: 21
title_name: "Food and Drugs"
section_number: "173.170"
section_name: "Aminoglycoside 3′-phosphotransferase II."
chapter_name: "FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "B"
subchapter_name: "FOOD FOR HUMAN CONSUMPTION"
part_number: "173"
part_name: "SECONDARY DIRECT FOOD ADDITIVES PERMITTED IN FOOD FOR HUMAN CONSUMPTION"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "21 U.S.C. 321, 342, 348."
regulatory_source: "42 FR 14526, Mar. 15, 1977, unless otherwise noted."
cfr_part: "173"
---
# 173.170 Aminoglycoside 3′-phosphotransferase II.
The food additive aminoglycoside 3′-phosphotransferase II may be safely used in the development of genetically modified cotton, oilseed rape, and tomatoes in accordance with the following prescribed conditions:
(a) The food additive is the enzyme aminoglycoside 3′-phosphotransferase II (CAS Reg. No. 58943-39-8) which catalyzes the phosphorylation of certain aminoglycoside antibiotics, including kanamycin, neomycin, and gentamicin.
(b) Aminoglycoside 3′-phosphotransferase II is encoded by the *kan*
<sup>r</sup> gene originally isolated from transposon Tn*5* of the bacterium *Escherichia coli.*
(c) The level of the additive does not exceed the amount reasonably required for selection of plant cells carrying the *kan*
<sup>r</sup> gene along with the genetic material of interest.
[59 FR 26711, May 23, 1994]