Lysine is catabolized to 2-aminoadipic acid in Penicillium chrysogenum by an omega-aminotransferase and to saccharopine by a lysine 2-ketoglutarate reductase. Characterization of the omega-aminotransferase

Abstract

The biosynthesis and catabolism of lysine in Penicillium chrysogenum is of great interest because these pathways provide 2-aminoadipic acid, a precursor of the tripeptide delta-L-2-aminoadipyl-L-cysteinyl-D-valine that is an intermediate in penicillin biosynthesis. In vivo conversion of labelled L-lysine into two different intermediates was demonstrated by HPLC analysis of the intracellular amino acid pool. L-lysine is catabolized to 2-aminoadipic acid by an omega-aminotransferase and to saccharopine by a lysine-2-ketoglutarate reductase. In lysine-containing medium both activities were expressed at high levels, but the omega-aminotransferase activity, in particular, decreased sharply when ammonium was used as the nitrogen source. The omega-aminotransferase was partially purified, and found to accept L-lysine, L-ornithine and, to a lesser extent, N-acetyl-L-lysine as amino-group donors. 2-Ketoglutarate, 2-ketoadipate and, to a lesser extent, pyruvate served as amino group acceptors. This pattern suggests that this enzyme, previously designated as a lysine-6-aminotransferase, is actually an omega-aminotransferase. When 2-ketoadipate is used as substrate, the reaction product is 2-aminoadipic acid, which contributes to the pool of this intermediate available for penicillin biosynthesis. The N-terminal end of the purified 45-kDa omega-aminotransferase was sequenced and was found to be similar to the corresponding segment of the OAT1 protein of Emericella (Aspergillus) nidulans. This information was used to clone the gene encoding this enzyme.

The inducers 1,3-diaminopropane and spermidine cause the reprogramming of metabolism in Penicillium chrysogenum, leading to multiple vesicles and penicillin overproduction

“…These two enzymes are ω-aminotransferases acting on ω-aldehydes. Biochemical studies using purified enzymes of P. chrysogenum showed that those enzymes are essential for the conversion of α-aminoadipic semialdehyde into lysine and vice versa [31] (see Discussion).…”

Repurposed HisC Aminotransferases Complete the Biosynthesis of Some Methanobactins

“…Instead, like the HisC-derived MbnNs, these enzymes are repurposed class III ω-aminotransferases, 36 which perform transamination reactions on a wide range of substrates, including ornithine, lysine, 4-aminobutyrate, adenosylmethionine-8-amino-7-oxaononanoate, alanine, and aspartate. The top non-Mbn-related BLAST results for this group IV aminotransferase are encoded within proteobacterial operons related to amino acid catabolism, including genes for ABC amine and peptide importers and additional enzymes supporting a role in the metabolism or catabolism of aminecontaining amino acids (lysine 37 and arginine) or related compounds (GABA, 38 ornithine, 39 and biotin 40 ). The reactions catalyzed by the group IV aminotransferases are likely to be quite distinct from the reactions performed by their close homologues, just as observed with the group I MbnN and the HisC-like aminotransferases.…”

A subfamily of PLP-dependent enzymes specialized in handling terminal amines

“…Often the aminotransferases of the AT-II group are also referred to as ω-transaminases (ω-ATs; [17,18,[21][22][23]). Indeed the physiological reactions of these enzymes almost invariably involve a terminal amino group or at least (e.g., in the cases of ABS or FUMAT) an amino group not located in α-position with respect to a carboxylate (Table 1); compounds containing such groups can be broadly described as ω-amines [13] 1 .…”