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You've arrived at the supermarket, and your trolley token is missing. It's not where you usually keep it - on your keyring, or in your bag. Flustered, you search for something to replace it. A coin of sorts. What you find, thank goodness, fits. So, you pull your trolley away from its fellow partners feeling both relieved and gratified. What you have just done is put something right that could have gone wrong. And you did it by way of an intermediate that mimicked what lacked. Situations such as these sometimes occur inside us. Enzymes may be temporarily out of order - not because something has gone wrong with them but because their substrate is lacking. As a result, they do nothing. This has been shown to happen to UXS1, an enzyme involved in forming part of our extracellular matrix which is crucial to our well-being. In the absence of an intermediate compound (UDP-4-ketoxylose), UXS1 remains inactive - which can create downstream complications. However, researchers discovered that a second enzyme, TGDS, comes to the rescue by producing an intermediate (UDP-4-keto-6-deoxyglucose) that is able to replace the one that is missing. UXS1 is thus revived and can resume its role.
