MPEP § 2412.03(c) — “Modified Amino Acid” (Annotated Rules)

§2412.03(c) “Modified Amino Acid”

USPTO MPEP version: BlueIron's Update: 2025-12-31

This page consolidates and annotates all enforceable requirements under MPEP § 2412.03(c), including statutory authority, regulatory rules, examiner guidance, and practice notes. It is provided as guidance, with links to the ground truth sources. This is information only, it is not legal advice.

“Modified Amino Acid”

This section addresses “Modified Amino Acid”. Primary authority: 37 CFR 1.831(b) and 37 CFR 1.831. Contains: 2 requirements, 2 prohibitions, 4 guidance statements, 1 permission, and 1 other statement.

Key Rules

Topic

Sequence Listing Content

8 rules
StatutoryInformativeAlways
[mpep-2412-03-c-7cc2211a6b180b41e4172b9a]
Requirement for Sequence Disclosure
Note:
This rule requires applications with a filing date on or after July 1, 2022, to disclose one or more nucleotide and/or amino acid sequences as defined in 37 CFR 1.831(b).

[Editor Note: This section is applicable to all applications with a filing date, or, for national phase applications, an international filing date, on or after July 1, 2022, having disclosure of one or more nucleotide and/or amino acid sequences as defined in 37 CFR 1.831(b). Formatting representations of XML (eXtensible Markup Language) elements in this section appear different than shown in Standard ST.26, which may be accessed at: www.wipo.int /export/sites/www/ standards/en/pdf/03-26-01.pdf.]

Jump to MPEP Source · 37 CFR 1.831(b)Sequence Listing ContentSequence Listing RequirementsSequence Listing Format
StatutoryInformativeAlways
[mpep-2412-03-c-a8e0bdca1ec78fa302734833]
Definition of Modified Amino Acid Excluding Common Ones
Note:
Defines a modified amino acid as any amino acid except the 19 standard ones listed.

WIPO Standard ST.26, paragraph 3(e), defines “modified amino acid” to mean any amino acid as described in the definition of “amino acid”, other than L-alanine, L-arginine, L-asparagine, L-aspartic acid, L-cysteine, L-glutamine, L-glutamic acid, L-glycine, L-histidine, L-isoleucine, L-leucine, L-lysine, L-methionine, L-phenylalanine, L-proline, L-pyrrolysine, L-serine, L-selenocysteine, L-threonine, L-tryptophan, L-tyrosine, or L-valine. See MPEP § 2412.03(b).

Jump to MPEP Source · 37 CFR 1.831Sequence Listing ContentSequence Listing FormatSequence Listing Requirements
StatutoryProhibitedAlways
[mpep-2412-03-c-4d87d4a6294cfc6fefa6aa70]
Modified Amino Acids Must Be Represented as X
Note:
Any modified amino acid that cannot be represented by a symbol in Table 3 must be denoted by 'X' in the sequence listing.

Modified amino acids, including D-amino acids, should be represented in the sequence as the corresponding unmodified amino acids whenever possible. Any modified amino acid in a sequence that cannot otherwise be represented by a symbol set forth in Table 3 must be represented by “X”, i.e., an “other” amino acid.

Jump to MPEP Source · 37 CFR 1.831Sequence Listing ContentSequence Listing FormatSequence Listing Requirements
StatutoryRequiredAlways
[mpep-2412-03-c-711614b90b27f9550d245a3f]
Modified Amino Acid Must Be Described in Feature Table
Note:
A modified amino acid must be described using a feature table with specific keys and qualifiers as outlined by MPEP § 2413.01(g).

A modified amino acid must be further described in a feature table. See MPEP § 2413.01(g), subsection I, for discussion of a “feature table”. Where applicable, the feature keys “CARBOHYD” or “LIPID” should be used together with the qualifier “note”. The feature key “MOD_RES” should be used for other post-translationally modified amino acids together with the qualifier “note”. The feature key “SITE” together with the qualifier “note” should be used when the modified amino acid is not a post-translationally modified amino acid. See MPEP § 2413.01(g), subsections II and III, for discussion of a “feature key”. The value for the qualifier “note” must either be an abbreviation set forth in Table 4 below or the complete, unabbreviated name of the modified amino acid. The abbreviations set forth in Table 4 or the complete, unabbreviated names must not be used in the sequence itself.

Jump to MPEP Source · 37 CFR 1.831Sequence Listing ContentSequence Listing RequirementsSequence Listing Format
StatutoryRecommendedAlways
[mpep-2412-03-c-f11eb7c6b08073bdd87a43c6]
Modified Amino Acid Feature Keys Must Include Note Qualifier
Note:
When describing modified amino acids, the feature keys ‘CARBOHYD’ or ‘LIPID’ must be used with the qualifier ‘note’, and other post-translationally modified amino acids should use the key ‘MOD_RES’ with a note qualifier.

A modified amino acid must be further described in a feature table. See MPEP § 2413.01(g), subsection I, for discussion of a “feature table”. Where applicable, the feature keys “CARBOHYD” or “LIPID” should be used together with the qualifier “note”. The feature key “MOD_RES” should be used for other post-translationally modified amino acids together with the qualifier “note”. The feature key “SITE” together with the qualifier “note” should be used when the modified amino acid is not a post-translationally modified amino acid. See MPEP § 2413.01(g), subsections II and III, for discussion of a “feature key”. The value for the qualifier “note” must either be an abbreviation set forth in Table 4 below or the complete, unabbreviated name of the modified amino acid. The abbreviations set forth in Table 4 or the complete, unabbreviated names must not be used in the sequence itself.

Jump to MPEP Source · 37 CFR 1.831Sequence Listing ContentSequence Listing RequirementsSequence Listing Format
StatutoryRecommendedAlways
[mpep-2412-03-c-75f9f54f8963942694cc64b7]
Requirement for Describing Modified Amino Acids
Note:
Use the feature key 'MOD_RES' with 'note' to describe post-translationally modified amino acids in a sequence listing.

A modified amino acid must be further described in a feature table. See MPEP § 2413.01(g), subsection I, for discussion of a “feature table”. Where applicable, the feature keys “CARBOHYD” or “LIPID” should be used together with the qualifier “note”. The feature key “MOD_RES” should be used for other post-translationally modified amino acids together with the qualifier “note”. The feature key “SITE” together with the qualifier “note” should be used when the modified amino acid is not a post-translationally modified amino acid. See MPEP § 2413.01(g), subsections II and III, for discussion of a “feature key”. The value for the qualifier “note” must either be an abbreviation set forth in Table 4 below or the complete, unabbreviated name of the modified amino acid. The abbreviations set forth in Table 4 or the complete, unabbreviated names must not be used in the sequence itself.

Jump to MPEP Source · 37 CFR 1.831Sequence Listing ContentSequence Listing RequirementsSequence Listing Format
StatutoryRecommendedAlways
[mpep-2412-03-c-c1a7386aad96ab8589b4f598]
Use Feature Key SITE for Non-Post-Translational Modified Amino Acids
Note:
When describing a modified amino acid that is not post-translationally modified, the feature key 'SITE' with the qualifier 'note' must be used.

A modified amino acid must be further described in a feature table. See MPEP § 2413.01(g), subsection I, for discussion of a “feature table”. Where applicable, the feature keys “CARBOHYD” or “LIPID” should be used together with the qualifier “note”. The feature key “MOD_RES” should be used for other post-translationally modified amino acids together with the qualifier “note”. The feature key “SITE” together with the qualifier “note” should be used when the modified amino acid is not a post-translationally modified amino acid. See MPEP § 2413.01(g), subsections II and III, for discussion of a “feature key”. The value for the qualifier “note” must either be an abbreviation set forth in Table 4 below or the complete, unabbreviated name of the modified amino acid. The abbreviations set forth in Table 4 or the complete, unabbreviated names must not be used in the sequence itself.

Jump to MPEP Source · 37 CFR 1.831Sequence Listing ContentSequence Listing RequirementsSequence Listing Format
StatutoryRequiredAlways
[mpep-2412-03-c-abe0228e5e7b02065cedcaec]
Note Must Be Abbreviation or Full Name of Modified Amino Acid
Note:
The qualifier 'note' must use abbreviations from Table 4 or the full name of post-translationally modified amino acids.

A modified amino acid must be further described in a feature table. See MPEP § 2413.01(g), subsection I, for discussion of a “feature table”. Where applicable, the feature keys “CARBOHYD” or “LIPID” should be used together with the qualifier “note”. The feature key “MOD_RES” should be used for other post-translationally modified amino acids together with the qualifier “note”. The feature key “SITE” together with the qualifier “note” should be used when the modified amino acid is not a post-translationally modified amino acid. See MPEP § 2413.01(g), subsections II and III, for discussion of a “feature key”. The value for the qualifier “note” must either be an abbreviation set forth in Table 4 below or the complete, unabbreviated name of the modified amino acid. The abbreviations set forth in Table 4 or the complete, unabbreviated names must not be used in the sequence itself.

Jump to MPEP Source · 37 CFR 1.831Sequence Listing ContentSequence Listing RequirementsSequence Listing Format
Topic

Sequence Listing Format

3 rules
StatutoryPermittedAlways
[mpep-2412-03-c-3fed74e70bd39e5119ba0fc6]
XML Element Formatting for Sequence Listings Required
Note:
This rule requires the proper formatting of XML elements in sequence listings for applications filed on or after July 1, 2022.

[Editor Note: This section is applicable to all applications with a filing date, or, for national phase applications, an international filing date, on or after July 1, 2022, having disclosure of one or more nucleotide and/or amino acid sequences as defined in 37 CFR 1.831(b). Formatting representations of XML (eXtensible Markup Language) elements in this section appear different than shown in Standard ST.26, which may be accessed at: www.wipo.int /export/sites/www/ standards/en/pdf/03-26-01.pdf.]

Jump to MPEP Source · 37 CFR 1.831(b)Sequence Listing FormatSequence Listing ContentSequence Listing Requirements
StatutoryRecommendedAlways
[mpep-2412-03-c-73311a54ccdba367efb6a55e]
Modified Amino Acids Must Be Represented as Unmodified
Note:
Any modified amino acid in a sequence should be represented by the corresponding unmodified amino acid whenever possible, and must be represented by 'X' if it cannot be otherwise symbolized.

Modified amino acids, including D-amino acids, should be represented in the sequence as the corresponding unmodified amino acids whenever possible. Any modified amino acid in a sequence that cannot otherwise be represented by a symbol set forth in Table 3 must be represented by “X”, i.e., an “other” amino acid.

Jump to MPEP Source · 37 CFR 1.831Sequence Listing FormatSequence Listing RequirementsSequence Listing Content
StatutoryProhibitedAlways
[mpep-2412-03-c-3ebbdef1403f23eecdbbfdae]
Abbreviations Not Allowed in Sequence
Note:
Modified amino acid abbreviations from Table 4 must be described fully and not used within the sequence itself.

A modified amino acid must be further described in a feature table. See MPEP § 2413.01(g), subsection I, for discussion of a “feature table”. Where applicable, the feature keys “CARBOHYD” or “LIPID” should be used together with the qualifier “note”. The feature key “MOD_RES” should be used for other post-translationally modified amino acids together with the qualifier “note”. The feature key “SITE” together with the qualifier “note” should be used when the modified amino acid is not a post-translationally modified amino acid. See MPEP § 2413.01(g), subsections II and III, for discussion of a “feature key”. The value for the qualifier “note” must either be an abbreviation set forth in Table 4 below or the complete, unabbreviated name of the modified amino acid. The abbreviations set forth in Table 4 or the complete, unabbreviated names must not be used in the sequence itself.

Jump to MPEP Source · 37 CFR 1.831Sequence Listing FormatSequence Listing RequirementsSequence Listing Content

Citations

Primary topicCitation
Sequence Listing Content
Sequence Listing Format
37 CFR § 1.831(b)
Sequence Listing ContentMPEP § 2412.03(b)
Sequence Listing Content
Sequence Listing Format
MPEP § 2413.01(g)

Source Text from USPTO’s MPEP

This is an exact copy of the MPEP from the USPTO. It is here for your reference to see the section in context.

BlueIron Last Updated: 2025-12-31