Interrogating the Tailoring Steps of Pactamycin Biosynthesis and Accessing New Pactamycin Analogues

Abstract

Pactamycin is a bacteria-derived aminocyclitol antibiotic with a wide-range of biological activity. Its chemical structure and potent biological activities have made it an interesting lead compound for drug discovery and development. Despite its unusual chemical structure, many aspects of its formation in nature remain elusive. Using a combination of genetic inactivation and metabolic analysis, we investigated the tailoring processes of pactamycin biosynthesis in Streptomyces pactum. The results provide insights into the sequence of events during the tailoring steps of pactamycin biosynthesis and explain the unusual production of various pactamycin analogues by S. pactum mutants. We also identified two new pactamycin analogues that have better selectivity indexes than pactamycin against malarial parasites.

Functional Characterization of 3‐Aminobenzoic Acid Adenylation Enzyme PctU and UDP‐N‐Acetyl‐d‐Glucosamine: 3‐Aminobenzoyl‐ACP Glycosyltransferase PctL in Pactamycin Biosynthesis

“…The late stage of the biosynthetic pathway of pactamycin has been characterized by Mahmud and co‐workers (Scheme bottom reaction steps) . They constructed various mutant strains of S. pactum , which accumulated intermediates of pactamycin biosynthesis, to propose the biosynthetic pathway.…”

“…They constructed various mutant strains of S. pactum , which accumulated intermediates of pactamycin biosynthesis, to propose the biosynthetic pathway. A double‐knockout mutant of ptmH ( pctJ ), which encodes a cobalamin‐dependent radical S ‐adenosyl‐ l ‐methionine (SAM) methyltransferase, and ptmD ( pctF ), which encodes a SAMdependent N ‐methyltransferase, was shown to accumulate TM‐101, a supposed intermediate of pactamycin biosynthesis . Cytochrome P450 oxygenase PtmY (PctA) seems to be involved in the hydroxylation reaction of late‐stage biosynthesis, although disruptive mutations of ptmY ( pctA ) do not completely abolish pactamycin production .…”

NAD+‐Dependent Dehydrogenase PctP and Pyridoxal 5′‐Phosphate Dependent Aminotransferase PctC Catalyze the First Postglycosylation Modification of the Sugar Intermediate in Pactamycin Biosynthesis

“…However, 3AAP was not incorporated into pactamycin; this indicated that the physiological substrate of PctL was 3ABA or its thioester derivatives such as 3‐aminophenyl‐β‐oxopropanoic acid thioester, which would undergo hydrolysis and decarboxylation to give the 3AAP moiety . Mahmud and co‐workers reported that a mutant with a knockout of a discrete acyl carrier protein PtmL (PctK) did not accumulate any pactamycin biosynthetic intermediates . Because no biosynthetic intermediate between 3ABA and TM‐101 has so far been isolated, the intermediates in the early stage of biosynthesis seem to be hydrophilic thioesters with acyl carrier protein (ACP; Scheme ).…”

Design, Synthesis, and Evaluation of α‐(Hydroxymethyl)cycloalkanols

“…However, in 2011, TM‐025 1 b , obtained by bioengineering, exhibited an improved profile displaying a greater cytotoxicity against Plasmodium falciparum as compared to mammalian cells. Similarly, Jogyamycin 1 c , another natural product analogue, showed potent antimalarial and antitrypanosomal activities, with IC 50 values of 1.5 and 12.3 nM, respectively [4–5] . These analogues, including de‐6MSA‐pactamycin 1 d , are structurally less complex and more stable than pactamycin 1 a .…”