Meat quality of pork is attracting more and more attention of consumers in recent years, a major determinant of which is intramuscular fat (IMF) content that influences the sensory quality traits like taste, flavor, water holding capacity and shear force [[1], [2], [3]]. As an indigenous fatty pig breed distributed in North China, the Laiwu pig is characterized by an extremely high level of IMF content (9% ∼ 12%), much higher than that in western lean-type pigs, such as Duroc, Yorkshire and Landrance pigs, with IMF being <2.5% [1,4]. At the fastest fat-deposition stage in the longissimus dorsi (LD) muscle of Laiwu pigs, from 120 d to 240 d, the IMF content of porcine LD muscle increased from 3.59% to 9.88% [1]. In our previous study on Laiwu pigs, we identified 52 differentially abundant proteins (DAPs) that are related to lipid deposition in the LD muscle between 120 d and 240 d [1]. However, for proteins, the precursor proteins are usually inactive and require a series of post-translational modifications (PTMs) to perform functions [5]. PTMs involve changes in formation of chemical bonds, resulting in alterations in protein conformation and subsequent allosteric modulation, thereby increasing the complexity of the proteome [5,6].

The malonylation of proteins is a highly conservative modification occurring on lysine residues. This modification was first identified in the study of histones by the Yingming Zhao research group at the University of Chicago [7]. Malonylation increases the hydrophobicity and volume of the side chain and affects the binding of enzymes with their targets [[6], [8]]. Malonyl-CoA, which adds the malonyl group to lysine residue leading to a change from +1 charge to −1 of the targeted lysine, plays an important role in occurrence of malonylation [7]. Acetyl-CoA carboxylase (ACC1 and ACC2) and acyl-CoA synthetase family member 3 (ACSF3) are critical enzymes in synthesis of malonyl-CoA [6].

ACOTs (acyl-CoA thioesterases) can hydrolyze the acyl CoA into unesterified fatty acids and CoA to regulate the generation of fatty acids and CoA in cells [[9], [10], [11]]. ACOT7, a member of ACOTs, also known as BACH, is expressed in various tissues and uses arachidonoyl-CoA as its preferred substrate [12,13]. Additionally, ʻHotDogʼ fold domains in N and C termini of ACOT7 are important for catalyzing thioester hydrolysis of fatty acid metabolism [12]. However, there is no report on the function of ACOT7 malonylation in regulating IMF deposition up to present.

In this study, by using pan-antibody, we first detected the differences of multiple PTMs in the total level of protein in the LD muscle between 120 d and 240 d of Laiwu pigs and found a notable PTM type of malonylation. Based on this, using TMT (Tandem Mass Tag) -based quantitative modified proteome analysis, we further investigated the differences in malonylated protein profiles of LD muscle samples from 120 d to 240 d of development. Finally, we focused on the function of a differentially modified protein, ACOT7, in the process of fat deposition, and revealed an important enzyme in the modification of this protein.