KasQ an Epimerase Primes the Biosynthesis of Aminoglycoside Antibiotic Kasugamycin and KasF/H Acetyltransferases Inactivate Its Activity.

Rajesh Rattinam,Ning-Shian Hsu,Saeid Malek Zadeh,Jin-Ping Lin,Kuan-Hung Lin,Tsung-Lin Li,Zhe-Chong Wang,Yung-Lin Wang,Kamal Adhikari,R Sidick Basha

doi:10.3390/biomedicines10020212

Abstract

Kasugamycin (KSM), an aminoglycoside antibiotic, is composed of three chemical moieties: D-chiro-inositol, kasugamine and glycine imine. Despite being discovered more than 50 years ago, the biosynthetic pathway of KSM remains an unresolved puzzle. Here we report a structural and functional analysis for an epimerase, KasQ, that primes KSM biosynthesis rather than the previously proposed KasF/H, which instead acts as an acetyltransferase, inactivating KSM. Our biochemical and biophysical analysis determined that KasQ converts UDP-GlcNAc to UDP-ManNAc as the initial step in the biosynthetic pathway. The isotope-feeding study further confirmed that 13C, 15N-glucosamine/UDP-GlcNH2 rather than glucose/UDP-Glc serves as the direct precursor for the formation of KSM. Both KasF and KasH were proposed, respectively, converting UDP-GlcNH2 and KSM to UDP-GlcNAc and 2-N’-acetyl KSM. Experimentally, KasF is unable to do so; both KasF and KasH are instead KSM-modifying enzymes, while the latter is more specific and reactive than the former in terms of the extent of resistance. The information gained here lays the foundation for mapping out the complete KSM biosynthetic pathway.

Highlights

Kasugamycin (KSM), an aminoglycoside antibiotic produced by Streptomyces kasugaensis, was discovered in 1965
A number of new findings revealed that KSM possesses several unexpected biological activities effectively countering some recalcitrant human diseases: (i) an in vitro and in vivo study showed that the combination of KSM with rifamycin is in a position to control Mycobacterium tuberculosis, [5] (ii) KSM was recently shown to be capable of inhibiting herpes simplex virus-2 (HSV-2), [6] and (iii) KSM has been shown to have a promising activity against COVID-19 by inhibiting 3a-channel [7] and chitinase 3-like-1 (CHI3L1) proteins [8]
A number of new findings have highlighted that KSM is a promising drug lead, as it effectively counters some recalcitrant human diseases [5–8]

Summary

Introduction

Kasugamycin (KSM), an aminoglycoside antibiotic produced by Streptomyces kasugaensis, was discovered in 1965. It has long been known that KSM binds specially to the interface between E- and P-site of the 30S ribosomal subunit to control fungal and bacterial protein translation [3]. KSM was used as an agricultural supplement to protect rice from fungus-derived diseases [4]. A number of new findings revealed that KSM possesses several unexpected biological activities effectively countering some recalcitrant human diseases: (i) an in vitro and in vivo study showed that the combination of KSM with rifamycin is in a position to control Mycobacterium tuberculosis, [5] (ii) KSM was recently shown to be capable of inhibiting herpes simplex virus-2 (HSV-2), [6] and (iii) KSM has been shown to have a promising activity against COVID-19 by inhibiting 3a-channel [7] and chitinase 3-like-1. We were attracted by these new findings and eager to investigate the biosynthetic pathway of KSM in the hope of generating new and useful KSM analogs in the future

Methods

Results

Conclusion