BIOTECHNOLOGICALLY RELEVANT ENZYMES AND PROTEINS In vitro and in silico evaluation of the inhibitory effect of a curcumin-based oxovanadium (IV) complex on alkaline phosphatase activity and bacterial biofilm formation G. Katsipis 1 & V. Tsalouxidou 1 & E. Halevas 2 & E. Geromichalou 3 & G. Geromichalos 1 & A. A. Pantazaki 1 Received: 13 August 2020 /Revised: 27 October 2020 /Accepted: 3 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract The scientific interest in the development of novel metal-based compounds as inhibitors of bacterial biofilm-related infections and alkaline phosphatase (ALP) deregulating effects is continuous and rising. In the current study, a novel crystallographically defined heteroleptic V(IV)-curcumin-bipyridine (V-Cur) complex with proven bio-activity was studied as a potential inhibitor of ALP activity and bacterial biofilm. The inhibitory effect of V-Cur was evaluated on bovine ALP, with two different substrates: para-nitrophenyl phosphate (pNPP) and adenosine triphosphate (ATP). The obtained results suggested that V-Cur inhibited the ALP activity in a dose-dependent manner (IC 50 = 26.91 ± 1.61 μM for ATP, IC 50 = 2.42 ± 0.12 μM for pNPP) exhibiting a mixed/competitive type of inhibition with both substrates tested. The evaluation of the potential V-Cur inhibitory effect on bacterial biofilm formation was performed on Gram (+) bacteria Staphylococcus aureus (S. aureus) and Gram (-) Escherichia coli (E. coli) cultures, and it positively correlated with inhibition of bacterial ALP activity. In silico study proved the binding of V- Cur at eukaryotic and bacterial ALP, and its interaction with crucial amino acids of the active sites, verifying complex’s inhibitory potential. The findings suggested a specific anti-biofilm activity of V-Cur, offering a further dimension in the importance of metal complexes, with naturally derived products as biological ligands, as therapeutic agents against bacterial infections and ALP- associated diseases. Key points • V-Cur inhibits bovine and bacterial alkaline phosphatases and bacterial biofilm formation. • Alkaline phosphatase activity correlates with biofilm formation. • In silico studies prove binding of the complex on alkaline phosphatase. Keywords Alkaline phosphatase . Oxovanadium complex . Curcumin . Bacterial biofilm . Escherichia coli . Staphylococcus aureus Introduction Phosphatases constitute a large heterogeneous group of en- zymes (Enzyme Commission (E.C.) 3.1.3) that hydrolyze phosphomonoesters into a phosphate ion (PO 4 3- (Pi)) and a molecule with a free hydroxyl group (Li et al. 2013). Alkaline phosphatases (ALPs) (Enzyme Commission (E.C.) 3.1.3.1) function as catalysts of the phosphate monoester hydrolysis at alkaline conditions. In humans, ALP activity has long been used as a serum indicator of health or disease states. Recently, the potential use of ALPs as a therapeutic target has emerged (Millán 2006). A number of inhibitors that can potentially modulate ALP activity for therapeutic benefit are currently under investigation since malfunction or overactivity of these G. Katsipis and V. Tsalouxidou contributed equally to this work. * A. A. Pantazaki natasa@chem.auth.gr 1 Laboratory of Biochemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 2 Institute of Biosciences & Applications, National Centre for Scientific Research “Democritus”, 15310 Athens, Greece 3 Laboratory of Pharmacology, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias Street, 11527 Athens, Greece Applied Microbiology and Biotechnology https://doi.org/10.1007/s00253-020-11004-0