Aggregation and Molecular Properties of β-Glucosidase Isoform II in Chayote (Sechium edule)

Abstract

The presence of isoforms of β-glucosidase has been reported in some grasses such as sorghum, rice and maize. This work aims to extract and characterize isoform II in β-glucosidase from S. edule. A crude extract was prepared without buffer solution and adjusted to pH 4.6. Contaminating proteins were precipitated at 4 °C for 24 h. The supernatant was purified by chromatography on carboxymethyl cellulose (CMC) column, molecular exclusion on Sephacryl S-200HR, and exchange anionic on QFF column. Electrophoretic analyzes revealed a purified enzyme with aggregating molecular complex on SDS-PAGE, Native-PAGE, and AU-PAGE. Twelve peptides fragments were identified by nano liquid chromatography-tandem mass spectrometry (nano LC-ESI-MS/MS), which presented as 61% identical to Cucurbita moschata β-glucosidase and 55.74% identical to β-glucosidase from Cucumis sativus, another Cucurbitaceous member. The relative masses which contained 39% hydrophobic amino acids ranged from 982.49 to 2,781.26. The enzyme showed a specificity to β-d-glucose with a Km of 4.59 mM, a Vmax value of 104.3 μM∙min−1 and a kcat of 10,087 μM∙min−1 using p-nitrophenyl-β-D-glucopyranoside. The presence of molecular aggregates can be attributed to non-polar amino acids. This property is not mediated by a β-glucosidase aggregating factor (BGAF) as in grasses (maize and sorghum). The role of these aggregates is discussed.

Biochemical Properties of Oregano b-Glucosidase Supports Origanum Onites L. as a Feed Additive

“…The K m value found for the enzyme as a substrate pNPG is considerably lower than -glucosidase purified from Aspergillus terreus (Yan et al, 2016), which catalyses soybean isoflavone hydrolysis with high efficiency and is recommended as an animal feed additive. The Vmax value of the purified enzyme, 1855 μM.min -1 for the pNPG substrate, is considerably higher than the V max value of Chayote -glucosidase isoform II (Cruz et al, 2020) and Brassica oleracea -glucosidase (Besic et al, 2017) against the same substrate. According to these results, it can be said that the enzyme's catalysis ability is similar to the enzymes recommended for soybean hydrolysis.…”