underacylated

Underacylated is an adjective used in biochemistry and molecular biology to describe a molecule that possesses fewer acyl groups than is typical, expected, or observed for that molecule. It most often refers to partial or incomplete acylation of a substrate, such as a protein or lipid, where acyl groups (for example acetyl, malonyl, succinyl, or fatty acyl chains) are less numerous than in the fully acylated form.

Context and examples: In proteins, lysine residues can undergo acylation. An underacylated protein has fewer acyl modifications, potentially due to limited donor molecules (acyl-CoA), reduced acyltransferase activity, or increased deacylation. In histones and other chromatin-associated proteins, underacylation can be associated with changes in regulatory interactions and gene expression, relative to more heavily acylated states. In lipid metabolism, underacylated lipids may reflect incomplete attachment of fatty acyl chains or altered lipid remodeling.

Measurement and interpretation: The degree of acylation can be quantified by mass spectrometry, chromatography, or antibody-based methods that distinguish acylated from non-acylated forms. Results are typically reported as the relative abundance of acylated species compared with the total pool, or as site-specific modification occupancy.

Causes and implications: Underacylation can arise from limited acyl donor availability, enzyme inhibition, altered cellular energetics, or increased activity of deacylating enzymes. Functionally, it can affect protein activity, stability, interactions, localization, and, in the case of histones, gene regulation.

See also: acylation, deacylation, acetylation, malonylation, lipidation, post-translational modification.