posted on 2020-03-20, 08:33authored byAnastasiya
V. Valueva, Roman S. Romanov, Nataliya N. Vorobyeva, Svetlana A. Kurilova, Elena V. Rodina
Pyrophosphate arthropathy is the
mineralization defect in humans
caused by the deposition of microcrystals of calcium pyrophosphate
dihydrate in joint tissues. As a potential therapeutic strategy for
the treatment of pyrophosphate arthropathy, delivery of exogenous
pyrophosphate-hydrolyzing enzymes, inorganic pyrophosphatases (PPases),
to the synovial fluid has been suggested. Previously, we synthesized
the conjugates of Escherichia coli PPase
(Ec-PPase) with detonation synthesis nanodiamonds (NDs) as a delivery
platform, obtaining the hybrid biomaterial retaining high pyrophosphate-hydrolyzing
activity in vitro. However, most known PPases including Ec-PPase in
the soluble form are strongly inhibited by Ca2+ ions. Because
synovial fluid contains up to millimolar concentrations of soluble
calcium, this inhibition might limit the in vivo application of Ec-PPase-based
material in joint tissues. In this work, we proposed other bacterial
PPases from Mycobacterium tuberculosis (Mt-PPase), which are resistant to the inhibition by Ca2+ ions, as an active PPi-hydrolyzing agent. We synthesized
conjugates of Mt-PPase with NDs and tested their activity under various
conditions. Unexpectedly, conjugates of both Ec-PPase and Mt-PPase
with aminated NDs retained significant hydrolytic activity in the
presence of well-known mechanism-based PPase inhibitors, fluoride
or calcium. The incomplete inhibition of PPases by fluoride or calcium
was found for the first time.