Talk:Luciferase

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Contents 1 Christmas Tree 2 Chemical compound 3 (an analog of muscle contraction) 4 Heat-shock

[edit] Christmas Tree

The tree thing seems to be quite old. What I've found dates back to 1999. Did anything ever happen? It was a cool idea and all but unless something panned out, I don't think it's encyclopedic. --jag123 15:20, 1 Jan 2005 (UTC) this is boring as shit

[edit] Chemical compound

Luciferase is an enzyme and not a chemical compound. --User:AAM | Talk 17:12, 18 April 2006 (UTC)

What part of the definition of a chemical compound does enzyme not fit? --Blainster 21:40, 18 April 2006 (UTC)

"A defining characteristic of a compound is that it has a chemical formula. Formulas describe the ratio of atoms in a substance, and the number of atoms in a single molecule of the substance (thus the formula for ethene is C2H4 rather than CH2). The formula does not indicate that a compound is composed of molecules; for example, sodium chloride (table salt, NaCl) is an ionic compound."

Enzymes do not have a fixed chemical formula, they have variable phosphorylations, ubiquitinations, sumoylations, glycosylations, myristylations etcetera. Does this convince you enough? --User:AAM | Talk 22:03, 18 April 2006 (UTC)

I agree - there are multiple forms of Luciferase - see Category:EC 1.13.12. A singly isolated luciferase could be described as a compound, but as a class of enzymes, they would best be described as a class of compounds.--Scienthomas 03:34, 19 April 2006 (UTC)

Any particular instance of an enzyme is, in fact, a chemical compound that "has a chemical formula". but I can agree with Scienthomas that an enzyme, more broadly taken, is a group or class of chemical compounds. To say an enzyme is not a chemical compound is like saying you are not made up of atoms because you are made of molecules. --Blainster 20:19, 19 April 2006 (UTC)

Would you argue that we ourselves should be classified as a group or class of chemical compounds as well, as we are composed of atoms? If we continue on that line then everything except a vacuum might classify as a chemical compound. --User:AAM | Talk 20:42, 19 April 2006 (UTC)

Here is another one: "A chemical compound is a chemical substance formed from two or more elements, with a fixed ratio determining the composition". Enzymes have definitely not a fixed ratio. Enzymes are classified by their EC numbers, not by a chemical formula --User:AAM | Talk 20:42, 19 April 2006 (UTC)

What is meant by saying fixed ratio, is to include the subset of polymers which do not have well defined MWs but do have a fixed ratio of elements. Of course enzymes are a type of "polymeric" compound that do have fixed MWs (assuming unbound substrates, subunits, etc). So we have compound -> polymer -> protein -> enzyme as increasingly specialized subsets of the class. Humans are clearly a mixture of various chemical compounds, but not a class because our diverse compounds are in the most general sense related more by proximity than by composition. To answer your question of how broadly to conceive chemical compounds, we can be much more specific than "everything except a vacuum". Plasmas certainly wouldn't qualify. To be a bit more serious, the salient points are: a compound is made up of 1) more than one element, and 2) with fixed ratio rather than amorphous composition. Proteins and enzymes satisfy both conditions. --Blainster 21:54, 19 April 2006 (UTC)

I forget about plasmas! But I insist that an enzyme has no fixed ratio as I said above. Without taking into account substrates (that are but for some exceptions only transiently associated anyway) and subunits, most enzymes, if not all, are variably modified (phosphate groups, ubiquitine groups, acetyl groups, methyl groups) and this makes that the ratio of elements varies. The Mw of a protein can also change in fonction of these modifications (do you want me to find an illustrating picture of this?). It would be interesting to 'find' the chemical formula of luciferase, then we could find out how this changes after some of the above mentioned modifications :-) --User:AAM | Talk 18:31, 20 April 2006 (UTC)

[edit] (an analog of muscle contraction)

Is this appropriate? ATP and calcium play a role in muscle contraction, but that doesn't make it an analogy. neffk 14:08, 5 September 2006 (UTC)

Indeed this part is very strange and does not give relevant information in my opinion. I removed the entire part, also on the Ca ions. Could the Ca ion part be substantiated by a reference than we can put it back. I do not know such reference. --User:AAM | Talk 18:08, 6 September 2006 (UTC)

The bioluminescent reaction between the luciferin complex, luciferase and oxygen is triggered by calcium ions. [1], and literature references therein. Journal discussions cite the muscle analogy. --Blainster 20:06, 6 September 2006 (UTC)

OK Renilla luciferase is catalyzed by Ca according to the literature. I think this should be specified in the text, as each luciferase and luciferin can have different caracteristics. Now it suggests that all luciferases are triggered by calcium and I don't think there is information on that. The mentioning of the analogy with muscle contraction sounds strange. The way it stands it sounds as if the chemical luciferase reaction is analogous to a contraction of a muscle, I agree with neffk that this seems not appropriate as analogy. Maybe a rewording could clarify this point if something more specific is meant? Perhaps than the exact reference for the muscle contraction could be mentioned in the text as well, this is not the case at this moment which makes it difficult to keep this information in the article. --User:AAM | Talk 20:18, 11 September 2006 (UTC)

[edit] Heat-shock

Luciferase is a very heat sensitive protein that is used in studies on protein denaturation, testing the protective capacities of heat shock proteins.

Okay, I'm going to preface this by saying I know, at best, a little more than the average person about biology, chemistry, and physics, so maybe this is just my stupidity. That said, as joe shmoe reading an encyclopedic entry, this statement is unclear to me. I have skimmed the sections on both heat-shock and denaturation, and it's unclear to me what is meant by the statement "very heat sensitive." Certainly, it means that Luciferase react in some extreme way to heat. But it's unclear to me whether that means that it reacts by heat killing it off, or to heat by causing it to multiply, or something else entirely. (I'm inclined to believe the first option, but...) Clarification would be great.--Sailor Titan (talk) 22:34, 5 February 2008 (UTC)