It's not entirely clear from the paper whether the blood fluids used were of rat or human origin. Rat metabolism can't be entirely reliably extrapolated onto human metabolism so it remains to be seen if the conversion of harmaline to harmine occurs
in vivo in human blood. There might be some metabolic studies on the fate of harmala alkaloids in ayahuasca users (I've not looked) but then it's worth noting that typical ayahuasca sample contain a preponderance of harmine and THH while, in contrast, having little in the way of harmaline content.
As far as enzymes go, one could in principle extract horseradish peroxidase from horseradish roots if purchasing from a biochemical supply house turned out to be too tricky.
Quote:Many materials have been explored to mimic natural HRP. For example, iron oxide nanoparticles and hemin-containing complexes have been used to mimic HRP.[12] These HRP-like artificial enzymes have been used for many applications, ranging from biomarker detection and tumor immunostaining to antibiofouling.
It might be a little much to go to the trouble of designing a custom enzyme mimic for this reaction but who knows?
“There is a way of manipulating matter and energy so as to produce what modern scientists call 'a field of force'. The field acts on the observer and puts him in a privileged position vis-à-vis the universe. From this position he has access to the realities which are ordinarily hidden from us by time and space, matter and energy. This is what we call the Great Work."
― Jacques Bergier, quoting Fulcanelli