Lysine Lactylation Writers: Enzymatic Versus Non-Enzymatic Mechanisms, Isomer Specificity, and Therapeutic Implications

Lysine lactylation (Kla) is a key modification linking cellular metabolism to epigenetic regulation, but its chemical nature is more complex than initially appreciated. It comprises two generation pathways differing in chirality and catalytic logic: enzymatic L-lactylation (KL-la) and non-enzymatic D-lactylation (KD-la). In 2024, breakthroughs in enantiomer-resolved techniques clarified their regulatory origins: KL-la is mainly driven by glycolytic flux, whereas KD-la depends on loss of function of the glyoxalase system. This chemical duality means that “who writes lactylation” is no longer a simple question of enzyme assignment but a highly context-dependent judgment. This review critically assesses functional evidence for the lactyl-CoA-dependent KAT family, the lactyl-AMP-dependent AARS family, and the non-canonical catalytic activity of HDACs. It analyzes in particular the substrate concentration paradox, the enantiomeric ambiguity of antibodies marketed as pan-Kla, and the causal confounding arising from shared enzymatic machinery between Kla and acetylation. On this basis, it constructs an integrated regulatory model centered on site-level net flux. Therapeutically, strategies targeting lactylation pathways show preliminary translational promise, but most interventions still perturb acetylation programs simultaneously. Future breakthroughs may depend on developing flux measurement tools, standardizing enantiomer-resolved detection, and shifting from single-target inhibition to strategies based on modification-profile stratification.