Urease immobilization on magnetic micro/nano-cellulose dialdehydes: Urease inhibitory of Biginelli product in Hantzsch reaction by urea.

Micro/nano celluloses (MC)/NC) were magnetized by nanoγ-Fe2O3 into the nanoγ-Fe2O3@MC (NMMC) and nanoγ-Fe2O3@NC (NMMC) which oxidized to NMMCD and NMNCD dialdehydes for Schiff-base immobilization of urease as NMMCD/urease and NMMCD/urease. The relative enzyme-activity of the immobilized ureases were comparable with the free-urease, although 75%-80% of the enzyme activity preserved for NMMCD/urease and NMNCD/urease after six cycles. The compared catalytic activities of the NMMCD/urease and NMMCD/urease in Biginelli/Hantzsch reactions in water at 60 °C surprised us by 100% selectivity for the Biginelli product 3,4-dihydropyrimidin-2(1H)-one (DHPM1). With the superiority of NMNCD/urease, this high selectivity using immobilized ureases is owing to the admirable urease inhibitory of the formed Biginelli product DHPM1 by urea condensation instead of urea hydrolysis. The robust enzyme inhibitory of the DHPM1 for free urease was also confirmed by phenol red test to show the deactivation of enzyme for enzymatic hydrolysis of urea and ammonia production in water.