How critical is the use of commercially available enzymes for selenium speciation?

Abstract

The aim of this work was to check whether commercially available enzymes are pure enough to be used for selenium speciation analysis and the contribution that impurities could make to Se determination in real samples. For this purpose, twelve commercially available enzymes with different origins and classifications (protease, amylase, cellulase, lipase) were analysed. After the dissolution of the enzyme in water, the Se species were separated by ion exchange chromatography, with inductively coupled plasma mass spectrometry used as the detection system. The results showed that the Se content was significant in several cases. The highest value was obtained for beta-amylase from barley, 3100 ng Se per g of enzyme. Speciation analysis showed that Se-methionine, selenite, selenate and some unknown compounds were present in several enzymes. In general, the Se species identified represented a small fraction of the total Se. For instance, only 17% of the total Se was determined for beta-amylase from barley. On the other hand, about 100% of the total Se was identified in protease from Streptomyces griseus. Upon comparing the results from different lots of the same enzyme, not all of them were found to be comparable. Thus, the presence of selenium species in commercially available enzymes could be due to the preparation procedure used for the enzyme; they could be present as degradation products. Therefore, when determining selenium species in samples with low Se contents, attention should be paid to enzyme purity in relation to selenium compounds when an enzyme is used for hydrolysis.

An evaluation of extraction techniques for arsenic in staple diets (fish and rice) utilising both classical and enzymatic extraction methods

“…One of the factors that contributes to both the poor mass balance and the poor recovering when using cellulase is the variable arsenic content of the enzyme itself. Our studies gave a sample procedural blank of 0.046± 0.003 µg g -1 As in the enzyme, which is in agreement with the work of Sanz et al (2005), Cuderman et al (2009) and Dufailly et al (2011). Cellulase is therefore not an appropriate extraction agent for the extraction of arsenic species in the selected CRM materials and rice samples.…”

Mycochemical Changes Induced by Selenium Enrichment in P. ostreatus Fruiting Bodies

“…The samples were incubated at 37 °C for 24 h, and then the samples were centrifuged at 1677 g for 10 min at 4 °C. The supernatant was recovered and passed through a 0.22 μm filter . The amino acids released after protease digestion were determined by HPLC-fluorescence using the Waters AccQ Tag Amino Acid Analysis method (Millipore Corp., Milford, MA, USA).…”

Selenium biotransformation by Saccharomyces cerevisiae and Saccharomyces bayanus during white wine manufacture: Laboratory-scale experiments

“…Blanks analysis were performed to evaluate the occurrence of seleno species (Se(VI) and SeMet) from impurities in the enzymes used for sample extraction (Cuderman & Stibilj, 2009). …”