Table 1 Physiological benefits of compartmentalization of β-lactam biosynthetic enzymes
| Physiological mechanisms. | Examples of benefitial effects |
|---|---|
| Sequestration of toxic intermediates or final products | Detoxification of phenylacetic or phenoxyacetic acid by transport into peroxisomes |
| Channeling of precursors or substrates for β-lactams biosynthesis away from primary metabolism | Storage of α-aminoadipic acid in vacuoles, away from the lysine biosynthetic pathway |
| Sequestration of intermediates for the temporal sequential formation of intermediates to final products | Temporal conversion of isopenicillin N into benzylpenicillin |
| Metabolic coupling of biosynthetic reactions and transfer of intermediates between co-localized enzymes | Putative coupling of ACVS and IPNS in the cytosol. Coupling of Phenylacetyl-CoA ligase and IPN acyl transferase Coupling of fatty acids catabolic and modifying enzymes |
| Localization in organelles having optimal pH or physiological conditions for the biosynthetic enzymes | IAT optimal activity at the pH values at peroxisomes Preservation of the thiol (-SH group) of the tripeptide under reduced redox conditions at the cytosol |
| Co-localization of enzymes in the membrane, or near the membrane of organelles for joint inclusion in transport vesicles for secretion | Protein assembly that includes VP16 and other proteins of the recognition/teethering membrane complex |
| Accumulation in vacuoles of proteins and intermediates to be degraded and recycled for biosynthesis of other metabolites | Colocalization of proteases and hydrolases in the vacuoles for recycling cellular materials |
| Formation of protein secretion complexes | Complexes facilitating secretion of secondary metabolites |