Hydrolysis of N-acetyl-L-glutamine by acylase I

Parenteral administration of N-acetyl-L-glutamine (NAQ) produces substantial urinary losses. To evaluate enteral utility, we examined NAQ hydrolysis by acylase I, a critical first step in biological utilization. NAQ was quantitatively hydrolyzed to glutamine in vitro. Enzyme kinetic parameters were compared for NAQ (Km = 11.4 mM, Vmax = 5.54 nmole glutamine/min/μg enzyme) and an approved food additive, N-acetyl-L-methionine (NAM) (Km = 1.36 mM, Vmax = 7.48 nmole methionine/min/μg enzyme). These data indicated preference for NAM in substrate recognition (Km), but similar relative catalytic ability (Vmax). While NAQ is possibly a suitable enteral glutamine source, utility will depend on intestinal acylase I levels and intestinal residence times not yet determined.