Scientists at the Institute of Bioscience and Biotechnology (IBBR; MD, USA) have detected plant enzyme traces in commercially available human blood protein samples previously believed to be pure. This has led to the suggestion that further purity tests, such as NMR screening, may be required for biotechnology products.
The team at the IBBR was researching the binding of various molecules to HSA, which constitutes around three to five percent of human blood. It is commonly used in cell growth media, which are used to manufacture proteins for several biotechnology and clinical applications. HSA is produced by genetically engineered rice seeds and is commercially available from multiple vendors.
During the course of their study, the IBBR scientists used NMR to search for certain chemical bonds between HSA and different molecules; however, the team found an unexpected result. Bonds in one of the tested molecules, ATP, were being broken – a reaction few enzymes are capable of facilitating. The researchers suspected that a group of plant enzymes called phytases may be responsible, given that they were using a plant-derived product.
The enzyme concentrations found in the study were too low to be detected by the current quality control tests employed by biotechnology manufacturers, which include ELISA as well as a combination of LC and MS. The IBBR chemists involved in the research, Robert Brinson and John Marino, suggested that the enzyme contamination could cause researchers to misinterpret experimental results based on cell cultures grown in HSA-based medium.
After their initial findings, the scientists then tested HSA products from four different vendors and discovered varying levels of phytase activity in each batch. Human serum-derived and yeast-derived HSA products were also tested, and the characteristic bond breaking was not observed.
Brinson and Marino also commented that NMR screening could provide an important quality control test for plant-produced biotechnology products to ensure that enzymes such as phytases do not end up in final products. Marino added: “It’s a very useful assay specifically tailored to plant production of these proteins.”
But Brinson also pointed out that the NMR screening would be an addition to, rather than a replacement for, standard methods: “What we’re trying to propose is that our NMR methods will directly complement what’s already being used.”