Mn2+ and Mg2+ improved sphingomyelinase production by Lactobacillus rhamnosus FTDC 8313 and binding affinity to sphingomyelin for generation of ceramides

• Mn2+ and Mg2+ enhanced sphingomyelinase activity via improved binding affinity.
• Maximum SMase activity of 6.54 mU ml−1 was produced from a combination of 0.65% MnSO4 and 0.82% MgSO4.
• Optimized L. rhamnosus FTDC8313 increased the conversion of sphingomyelin to ceramide in HaCaT cells.
• Altered availability of the two ions Mn2+ and Mg2+ reduced their effects on SMase activity.

The present research aims to optimize the sphingomyelinase (SMase) activity produced by Lactobacillus rhamnosus FTDC 8313 using divalent metal ions via response surface methodology and to further study the effects of the divalent metal ions on SMase activity using molecular modeling approach. This study also aimed to assess the possibility of increasing ceramide levels in vitro on cultured keratinocytes upon treatment with the extracellular extract of the optimized L. rhamnosus FTDC 8313. Using a central composite design, an optimum point of SMase activity (6.54 mU ml−1) was produced from a combination of 0.65% (w/v) MnSO4 and 0.82% (w/v) MgSO4. 3D response surface indicated that the altered availability of the two ions (Mn2+ and Mg2+) reduced their effects on SMase activity. In addition, the treatment of the HaCaT cells with optimized extracellular extract of L. rhamnosus FTDC8313 significantly increased (P < 0.05) the conversion of sphingomyelin to ceramide as compared to the control. Molecular docking demonstrated that the addition of Mn2+ and Mg2+ into the active site of SMase improved the binding affinity between the SMase and sphingomyelin based on its free energy of binding as well as the interaction distances between the important catalytic residues Glu53 and His296.