Purification and properties of 3′-phosphoadenosine-5′-phosphosulphate: Desulphoglucosinolate sulphotransferase from Brassica juncea cell cultures

Abstract

The enzyme 3′-phosphoadenosine-5′-phosphosulfate:desulphoglucosinolate sulphotransferase was partially purified from Brassica juncea cell cultures by fractional precipitation with ammonium sulphate, anion-exchange chromatography and gel filtration. The resulting enzyme preparation had a specific activity of ⋔ ∼ 2 nmol/hr mg protein, representing a 230-fold purification and an overall yield of 58%, compared with crude cell extract. The enzyme had no absolute requirements for cations, and was inhibited by various SH-group reagents. The enzyme was stable up to 40° for at least 1 hr. Maximum activity was exhibited between pH 8.5 and 9.0 at 30°. The enzyme had an apparent pI and M r of 4.84 and 44 000, respectively. The K r values for desulphobenzylglucosinolate (DSBG) and 3′-phosphoadenosine-5′-phosphosulphate (PAPS) were 2.3 and 0.78 μM, respectively. The enzyme did not sulphate DSBG in the presence of adenosine-5′-phosphosulphate. Product inhibition studies established that 3′-phosphoadenosine-5′-phosphate was competitive with PAPS ( K i 0.4 μM).