Xenorhabdus khoisanae SB10 produces Lys-rich PAX lipopeptides and a Xenocoumacin in its antimicrobial complex

BMC Microbiology

Table 2 Summary of the antimicrobial compounds in the three main absorbing fractions that were identified using UPLC-MS and UPLC-MS^e. PAX peptide identities and names are from Fuchs et al. [32]

Fraction	UPLC Rt (min)	m/z of major [M + H]⁺	Compound M_r^a	Theoretical M_r^b	Mass error (ppm)^c	Proposed compound identity
B	4.27	407.2182	406.2104	406.2104	0.0	Xenocoumacin 2 (C₂₁H₃₀N₂O₆)
B	2.93	1052.7948	1051.7870	1051.7845	2.4	PAX1’ (C₁₄H₂₇O₂)GK₆
C	3.18	1078.8119	1077.8041	1077.8001	3.7	PAX7E1* (C₁₆H₂₉O₂)GK₆
C	3.42	1070.8091	1069.7921	1069.7951	−2.8	PAX1L* (C₁₄H₂₉O₃)GK₆
D	3.29	1066.8097	1065.7965	1065.8001	−3.4	PAX3’ (C₁₅H₂₉O₂)GK₆
F	3.47	1054.8115	1053.8012	1053.8001	1.0	PAX1L-DH* (C₁₄H₂₉O₂)GK₆
	3.32, 3.47^#	1080.8286	1079.8191	1079.8158	3.1	PAX7 (C₁₆H₃₁O₂)GK₆
	3.71	1078.8096	1077.8002	1077.8001	0.1	PAX7E2* (C₁₆H₂₉O₂)GK₆
	3.88	1078.8070	1077.7979	1077.8001	−2.0	PAX7E3* (C₁₆H₂₉O₂)GK₆
G	2.51	1050.7723	1049.7623	1049.7688	−6.2	PAX5 (C₁₄H₂₅O₂)GK₆
	2.90	1052.7936	1051.7821	1051.7845	2.3	PAX1’ (C₁₄H₂₇O₂)GK₆
	3.57	1080.8280	1079.8161	1079.8158	0.3	PAX7 (C₁₆H₃₁O₂)GK₆
	3.83	1106.8412	1105.8294	1105.8314	−1.8	PAX8 (C₁₈H₃₃O₂)GK₆

^aExperimental monoisotopic M_r of compound was calculated using the TOF transform or MaxEnt3 function in the MassLynx 4.01 software package
^bTheoretical monoisotopic M_r of compound was calculated from accurate monoisotopic M_r of Lys =128.09496 and Gly = 57.02146, and monoisotopic A_r of O =15.9949146; H=1.0078250, N=14.0030740 and C=12.0000000
^cMass error in parts per million (ppm) = 10⁶×{M_r (theoretical) - M_r (experimental)}/ M_r (theoretical)
^#Early elution of broad peak, fronting and tailing due to aggregation at high concentration
*Putative identification as PAX peptides from peptide moiety fragments and accurate mass determination, E denotes an enoyl group, L denotes linear, DH denotes dehydroxylated, structure of R-group was not elucidated
Refer to Additional file 1 for UPLC-MS, ESMS and MS/MS data on all the compounds

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