Heasley C J, Fitzpatrick P F
Department of Biochemistry, Texas A&M University, College Station 77843-2128, USA.
Biochem Biophys Res Commun. 1996 Aug 5;225(1):6-10. doi: 10.1006/bbrc.1996.1122.
Nitroalkane oxidase from Fusarium oxysporum catalyzes the oxidation of nitroalkanes to aldehydes, transferring the electrons to oxygen to form hydrogen peroxide. The steady-state kinetic patterns have been determined with nitroethane, 1-nitropropane, and 1-nitropentane as substrates. In all three cases, the data fit best to a ping pong kinetic mechanism. The pH dependences of the V/K values for 1-nitropentane and phenylnitromethane show that an amino acid residue on the enzyme with a pKa-value of 6.7 must be unprotonated for activity with both substrates. A second group must be protonated for activity. The pKa value of this group matches the pKa values of the nitroalkanes, 9.3 with nitropropane and 6.7 with phenylnitromethane, establishing that the nitroalkane must be in the neutral rather than the anionic form for catalysis.
尖孢镰刀菌的硝基烷氧化酶催化硝基烷氧化为醛，将电子转移给氧以形成过氧化氢。以硝基乙烷、1-硝基丙烷和1-硝基戊烷为底物测定了稳态动力学模式。在所有三种情况下，数据最符合乒乓动力学机制。1-硝基戊烷和苯基硝基甲烷的V/K值对pH的依赖性表明，酶上pKa值为6.7的氨基酸残基必须去质子化才能对两种底物都具有活性。另一基团必须质子化才能具有活性。该基团的pKa值与硝基烷的pKa值相匹配，硝基丙烷的pKa值为9.3，苯基硝基甲烷的pKa值为6.7，这表明硝基烷必须以中性而非阴离子形式进行催化。
