WHEN medical emergencies arise, either due to large-scale disasters or disease outbreaks, hospitals and agencies such as the Red Cross are faced with a severe shortage of donor blood, especially due to the mismatch in blood types. Now scientists from the University of British Columbia claim that they have identified from the human gut enzymes that can turn type A and B blood into O, the universal blood type, 30 times more efficiently than the previously studied enzymes. These findings have been reported in “Nature Microbiology”.
When these findings were reported at the annual meeting of the American Chemical Society in August 2018, one of the authors, Stephen Withers, said: “We have been particularly interested in enzymes that allow us to remove the A or B antigens from red blood cells. If you can remove those antigens, which are just simple sugars, then you can convert A or B to O blood.” According to him, scientists have been pursuing this line of research for quite some time but without being able to find efficient and selective enzymes that are also safe and economical to do the job.
To assess potential enzyme candidates quickly, Withers and his collaborator used metagenomics. “With metagenomics, you take all of the organisms from an environment and extract the sum total DNA of those organisms all mixed up together,” Withers explained. Casting such a wide net allowed Withers’ team to sample the genes of millions of microorganisms without the need for individual cultures.
The researchers then used E.coli to select for DNA-containing genes that code for enzymes that can cleave sugar residues. So instead of using metagenomics as a means of studying microbial ecology, the scientists used it to discover new biocatalysts. “This is a way of getting that genetic information out of the environment and into the laboratory setting and then screening for the activity we are interested in,” Withers said.
Withers’ team sampled DNA from mosquitoes and leeches, organisms that degrade blood, but ultimately found successful candidate enzymes in the human gut microbiome itself. Some of the sugars of glycosylated proteins called mucins that line the gut wall are similar in structure to the antigens on A- and B-type blood.
The researchers zeroed in on the enzymes the bacteria use to pluck the sugars off mucin and found a new family of enzymes that are 30 times more effective at removing red blood cell antigens of A- and B-types than candidates that have been reported earlier.