Tag-free, specific conjugation of glycosylated IgG1 antibodies using microbial transglutaminase

Structural Insights into Lipoate Ligase A-Mediated Antibody Modifications

Enzyme-mediated site-specific protein modification is gaining attention in biopharmaceuticals due to its high specificity and mild conditions. Lipoic acid ligase A (LplA) has been widely studied for conjugating short-chain fatty acids to lysine residues, traditionally using LAP tags. Recent advances have enabled tag-free LplA modifications, expanding applications in antibody-drug conjugates (ADCs) and beyond. This study investigates the selective modification of Lys188 in trastuzumab by LplA. Spatial analysis and molecular modeling suggest that D151 and H189 facilitate nucleophilic attack and stabilize intermediates via electrostatic and π-cation interactions. These insights enhance our understanding of enzyme-driven site selectivity, guiding the rational design of antibody modifications. The findings support broader applications in ADC production, diagnostics, and next-generation biopharmaceuticals, emphasizing the role of local amino acid environments in enzymatic modifications.

Antibody Modification via Lipoic Acid Ligase A-Mediated Site-Specific Labeling

Enzymatic modification, particularly utilizing lipoic acid ligase (LplA), has emerged as a transformative approach in biopharmaceuticals, enabling precise and site-specific protein modifications. This review delves into the innovative applications of LplA in antibody modifications, including the creation of antibody-drug conjugates (ADCs) and the advancement of tag-free conjugation techniques. LplA's ability to facilitate the incorporation of bioorthogonal groups and its adaptability to various substrates underscores its versatility. Key developments include the successful generation of dual-labeled antibodies and the application of LplA in modifying antibody fragments. Additionally, the review explores the potential for LplA to enhance the therapeutic efficacy of ADCs through improved drug-to-antibody ratios and site-specific payload attachment. The implications of these advancements are significant, suggesting that LplA-mediated modifications could lead to more effective and targeted antibody-based therapies. This review aims to provide a comprehensive overview of LplA's role in expanding the possibilities of enzymatic conjugation, setting the stage for future research and clinical applications.

Transglutaminase-mediated proximity labeling of a specific Lys residue in a native IgG antibody

The fusion protein of an engineered zymogen of microbial transglutaminase (EzMTG) with a protein G variant, EzMTG-pG, enabled the proximity-based, tag-free labeling of Lys65 in the heavy chain of a native IgG antibody (trastuzumab) with a Gln-donor peptidyl substrate functionalized with a fluorescent molecule.

Tag-free protein modification by lipoate ligase A: exploring substrate tolerance

This study delves into the functional intricacies of lipoate ligase A (LplA), an enzyme showing great promise in bioconjugation due to its unique capacity for introducing azido groups into proteins without requiring a genetic tag. We aimed to enhance the understanding of LplA's functionality, particularly its substrate tolerance and the reliability of various analytical techniques. A pivotal aspect of our approach was incorporating azido groups into a range of proteins, followed by the addition of the fluorescent molecule Cy3 via click chemistry. Analysis of fluorescent intensity in the altered proteins indicated varying degrees of conjugation. Additionally, phenyl resin-based RP-HPLC facilitated effective separation of modified proteins, unmodified proteins, and remaining fluorescent tags post-separation. SASA analysis provided insights into conjugation trends, guiding the identification of proteins amenable to LplA's tag-free modification. Our findings demonstrate LplA's broad substrate tolerability for protein modification.

Analytical studies on the conjugation site specificity of trastuzumab modified by Escherichia coli lipoate ligase A: multiple-enzyme digestion approach for peptide mapping

Tag-free protein modification has received considerable attention in the field of chemical biology owing to the versatility and simplicity of the reaction sequence. In 2021, a novel tag-free enzymatic modification of antibodies utilizing lipoate ligase A (LplA) was reported to reveal its potential in the production of site-specific antibody conjugates. Primary peptide mapping analysis revealed the biased site specificity of antibodies modified by LplA; however, quantitative analysis remains challenging because of the complicated heterogeneity derived from biased selective modification. In an effort to further understand the site occupancy of LplA-modified antibodies, this study employed numerous unconventional techniques and strategies. Optimization of HPLC conditions and utilization of enzymes such as trypsin, Glu-C, and chymotrypsin significantly increased sequence data coverage. The transition from traditional spectral counting to a more accurate peak area-based label-free quantification helped better analyze peptide modification levels. The results obtained indicate that LplA-induced modifications are specific lysines, particularly the light chain Lys188/190 site, which have an increased modification rate compared to chemically induced modifications. This study not only contributes to the understanding of peptide modification, but also presents an improved methodology that promises to stimulate further research in this field.