Christian de Duve - Uricase: Not a typical enzyme (55/106) скачать в хорошем качестве

Christian de Duve - Uricase: Not a typical enzyme (55/106)

To listen to more of Christian de Duve’s stories, go to the playlist:    • Christian de Duve (Scientist)   Belgian biochemist Christian de Duve (1917-2013) was best known for his work on understanding and categorising subcellular organelles. He won the Nobel Prize in Physiology or Medicine in 1974 for his joint discovery of lysosomes, the subcellular organelles that digest macromolecules and deal with ingested bacteria. [Listener: Peter Newmark; date recorded: 2005] TRANSCRIPT: I want to go back to uricase. Urate oxidase, which... it's a long time since we mentioned it so let me remind you: urate oxidase was the sixth enzyme in 1955 that we had found to show the same distribution pattern as the other five. The other five were acid hydrolysis, typical lysosomal enzymes; uricase was an oxidising enzyme, is not a digestive enzyme, it was not latent, it had a ph optimum of seven – or more than seven, maybe nine, even, if I remember rightly – and so it was an odd enzyme to be in lysosomes. And so, as we continued this work and studied additional enzymes, we found two more enzymes that showed the same kind of distribution but were not typical acid hydrolyses... hydrolases. One was D-amino-acid oxidase, which again is an oxidising enzyme like urate oxidase but oxidises amino acids... D-amino acids, not the alkaline, the unnatural, so-called D-amino acids, and like urate oxidase converts oxygen to hydrogen peroxide in doing this. And the third enzyme we discovered having the same kind of distribution was a catalase, and catalase is an enzyme that can use hydrogen peroxide to oxidise... to peroxidase substances like ethanol or nitrate... nitrite, or it can use hydrogen peroxide to oxidise hydrogen peroxide, in which case it actually splits hydrogen peroxide in H2O, water and oxygen. So the three enzymes that we had have a connection by way of hydrogen peroxide to oxidases making hydrogen peroxide, catalase destroying it.