Crosstalk Between Lysine Lactylation and Acetylation Regulates Lactate Dehydrogenase in Streptococcus mutans

Post-translational modifications (PTMs) provide essential fine-tuning of protein functions in response to environmental changes. Among the PTMs, lysine acetylation (Kac) and the recently identified lysine lactylation (Kla) play crucial roles in metabolic regulation, as lactate and acetyl-CoA (Ac-CoA) are generated from pyruvate at the end of glycolysis. However, their crosstalk and regulatory mechanisms remain largely unknown, particularly in prokaryotes. Here, we investigated the intricate interrelation between Kla and Kac in the cariogenic bacterium Streptococcus mutans, a prolific producer of lactate. We conducted a comprehensive profiling of Kla and Kac, revealing their widespread distribution in glycolytic enzymes. Lactate dehydrogenase (LDH), the terminal enzyme of glycolysis, exhibited dynamic Kla and Kac shifts in line with glycolytic intermediates, with the Kla/Kac ratio reflecting the metabolic influx. Furthermore, ActA was pinpointed as a dual-function acyltransferase that catalyzes the Kla and Kac of LDH, both of which negatively regulate its enzymatic activity. Importantly, the study identified lysine 307 (K307) on LDH as a critical site, with its acylation significantly altering LDH activity, thereby affecting lactate production and bacterial growth. Our insights into the metabolic regulation mediated by Kla and Kac contribute to understanding the metabolism-PTM-metabolism feedback loop, allowing bacteria to fine-tune their metabolism in response to the availability of metabolic intermediates.