Aromatic Family: Tryptophan

00:02 The aromatic family is next stem we will consider, the synthesis of.

00:06 These include the amino acids: tryptophan, phenylalanine and tyrosine.

00:12 Each of these amino acids is derived from some very simple precursors.

00:17 Phosphoenolpyruvate which is an intermediate in the glycolysis pathway and erythrose-4-phosphate which is an intermediate from the pentose phosphate, phosphate pathway.

00:27 The synthesis pathways are complex.

00:29 And again, I'm not going to go into individual reactions other than to show you the schematic that we see here.

00:35 Each of the synthetic pathways involves the production of shikimic acid and chorismic acid.

00:40 We can see the chorismate or the chorismic acid in the schematic here.

00:44 Phenylalanine and tyrosine pathways overlap because tyrosine can be produced directly from phenylalanine.

00:51 It can also be produced independently of it as well.

00:55 Hormones and neurotransmitters are made from each of these amino acids.

00:59 So this aromatic family has a lot of connections to other things that cells need.

01:05 Now the synthesis of tryptophan is interesting.

01:07 Its regulated synthesis in bacteria has a very interesting mechanism known as attenuation.

01:14 Attenuation is a way of controlling an entire operon.

01:17 Now an operon is a set of five genes.

01:20 Making five genes takes a lot of energy.

01:23 So cells only want to be synthesizing those five genes to make tryptophan when tryptophan is itself needed.

01:29 If tryptophan is available, making those genes waste energy.

01:34 So they have involved a way of controlling whether or not those five genes are made or not made depending upon whether tryptophan is present or not present.

01:43 When tryptophan concentration is high, then the transcription of the operon to make those five genes actually aborts.

01:50 It starts, but it aborts.

01:53 That prevents these five genes from being made and saves energy because tryptophan is available.

01:59 When tryptophan supply is slow, that aborted process does not occur.

02:04 The entire transcription of the entire operon occurs.

02:07 So this process is attenuation.

02:09 Very interesting way of controlling synthesis of a set of genes.

02:15 The molecules made from tryptophan are shown in the screen here.

02:18 They include melatonin.

02:19 And melatonin is important for circadian rhythm sensing.

02:24 It affects our mood, it affects our sleep, affects our blood pressure.

02:28 Melatonin is used in some sleeping treatments actually.

02:33 The production of melatonin, we know now, is affected by blue light.

02:38 And the more blue light we have, especially later in the evening, the less melatonin we produce.

02:44 The less melatonin we produce, the more sleeping difficulty we have.

02:48 So one suggestion people have is not to use your computer monitor too much at night or to use a computer program that actually reduces the amount of blue light being produced by your computer screen.

03:00 Serotonin is what people refer to as the happy hormone.

03:03 It's a neurotransmitter.

03:04 It causes vasoconstriction, which actually increases blood pressure, and then enhances memory, learning and it's a contributor to happy feelings.

03:13 When you're feeling well, feeling happy, you're probably producing serotonin.

03:19 Niacin we can see is one of our vitamins.

03:21 It's known as vitamin B3.

03:24 It's important component of nicotinamide.

03:27 And nicotinamide is used to make NAD, NADH, NADP, and NADPH.

03:33 A deficiency of vitamin B3 is very severe and leads to the disease known as an pellagra.

03:40 The last of the molecules made from tryptophan is that the auxins.

03:43 There are families of molecules and indole-3-acetic acid is the most important and the most common one.

03:49 It is a plant hormone and was in fact the first plant hormone that was discovered.

03:54 It's used in plants to stimulate cell division and causes rooting in the plants.