Through what baroque anfractuous extraction, concatenation, and conglomeration, by what lexical catabolism and anabolism, do we have the pleasure of seeing this word? Are you sure you can even read it right at first glance? Loops and funnels and posts… two g’s four apart, two y’s four apart, three l’s two apart, widely separated i’s, and a spare t c ne. You may discern a gly and another gly separated by an l. Your eyes may feel that somehow the word has had a hiccup and restarted.
If you say the word, you will see that the /gl/ is essentially a coarticulation; your tongue is ready for the /l/ when you start saying the /g/ and it just releases to that, then touches again, stops, releases… It sounds like you’re drinking some kind of beverage.
And maybe if you are drinking something, or even if you’re not, somewhere in your body – in numerous locations in your body – tiglyglycine is being made and unmade along with a vast variety of other complex chemicals. The number of incredibly intricate chemical processes going on in your body every second, and the degree of their intricacy and complexity, is astounding, as is the fact that people seldom have serious breakdowns of this machine even though your wetware is orders of magnitude more complex than any bit of hardware ever built.
So what is tiglyglycine? The short answer is that it’s an intermediate product of the catabolism of isoleucine, which is an essential amino acid. I like this fuller answer from the Human Metabolome Database, which most of you will probably skip:
Tiglylglycine is an acyl glycine. Acyl glycines are normally minor metabolites of fatty acids. However, the excretion of certain acyl glycines is increased in several inborn errors of metabolism. In certain cases the measurement of these metabolites in body fluids can be used to diagnose disorders associated with mitochondrial fatty acid beta-oxidation. Acyl glycines are produced through the action of glycine N-acyltransferase (EC 18.104.22.168) which is an enzyme that catalyzes the chemical reaction: acyl-CoA + glycine < — > CoA + N-acylglycine. Tiglylglycine is an intermediate product of the catabolism of isoleucine. An elevated level of tiglylglycine is identified in urine of patients with beta-ketothiolase deficiency or with disorders of propionate metabolism.
So, OK, now we have some idea (maybe not all that much idea, depending on your knowledge of organic chemistry) of how the substance tiglyglycine is made. How about how the word tiglyglycine is made?
First you’ll see that the back half is glycine. Glycine is the simplext amino acid. It got its name from Greek γλυκύς glukus ‘sweet’ (the upsilons υ, which I transliterate from classical Greek as u, were rendered in Latin as y – by the time Latin took the words the sound had already started to move forward; in modern Greek, that letter by itself is said with an “ee” sound, though in diphthongs it’s different). The ine is from a Latin suffix for deriving abstract nouns and is quite common in organic chemistry.
In the front half, the tiglyl is actually made of the root tigl and the suffix yl. Yes, that’s right, that first gly was synthesized from heterogeneous parts and is not said like the second one. The suffix yl is commonly used in chemistry on radicals made of two or three elements; it comes from Greek ὕλη hulé ‘wood, matter, substance’ (also used to refer to the basic matter of the universe). From the same root we get the modern English word hyle.
And the tigl? From a flowering plant called croton. I’ll explain. Tiglic acid is found in (among other things) croton oil, i.e., the oil extracted from the croton. The Linnaean taxonomic name of croton is Croton tiglium. Now, croton is from κροτών kroton ‘tick’, but that doesn’t matter for our purposes except inasmuch as it’s the other half of the lexical molecule from which the tiglium detaches and is catabolyzed to tigl. The tiglium comes from Latin; croton seeds were called grana tiglia or grana tilli, and that tiglium or tillus may come from Greek τῖλος tilos ‘diarrhea’ in reference to the seeds’ ability to cause it.
So, do you follow? Tick diarrhea plant lends diarrhea part because of oil; diarrhea part is broken down at root and merged with reduced wood, and that is tacked onto sweet with a Latin suffix. Ah, well, word formation is, like body chemistry, an organic process.