This study investigated the turnover rates of acylated sugars in Mycobacterium smegmatis during growth on glucose. Using radioactively labeled [14C]glucose, researchers tracked incorporation into various cellular components. They found that acylated trehalose and acylated glucose turned over approximately 13 and 8 times per cell generation, respectively, while free trehalose turned over about 3 times. However, these acylated sugars represented only 0.2-3.8% of bacterial dry weight, indicating they are not major metabolic intermediates. In contrast, total lipids turned over more slowly, and polysaccharides and cell residue showed minimal turnover. The authors used mathematical modeling to calculate turnover numbers based on the time required for compounds to reach 50% specific activity relative to glucose in the medium. Their findings suggest acylated sugars are unlikely to serve primarily as storage compounds or major glucose transporters, despite their rapid turnover. The biological role of these compounds remains unclear, and the authors propose that further investigation using in vitro enzyme systems is needed to understand their function.

Key findings

• Acylated trehalose and acylated glucose turned over 13 and 8 times per cell generation respectively, much faster than free trehalose (3x) and total lipids
• Despite rapid turnover, acylated sugars comprised only 0.2-3.8% of bacterial dry weight, indicating they are not quantitatively major metabolic intermediates
• Free trehalose is likely not the direct precursor of acylated trehalose, suggesting either multiple trehalose pools or direct synthesis from trehalose phosphate
• The rapid turnover argues against a primary storage role for acylated sugars, as their breakdown was not tightly regulated despite high glucose availability