tag:blogger.com,1999:blog-37148773.post6835442446168410576..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: Fixing Carbon: Building a Better RubiscoLarry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-37148773.post-38476053243201318272010-05-05T09:14:08.181-04:002010-05-05T09:14:08.181-04:00i've come across two reasons for why the oxyge...i've come across two reasons for why the oxygenase activity of Rubisco might be a good thing:<br /><br />1. leads to fixed nitrogen<br />2. protects photosystems from light damage by recycling reducing cofactor NADH.<br /><br />These are advantages for non-cultivated crops, but in controlled conditions could remove oxygenase activity and increase efficiency.<br /><br />PS. How about engineering a rubisco that accepts a bicarbonate ion instead of CO2 (as PEP carboxylase does in C$ plants?<br /><br />Cheers,<br />BobAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-55199333726487804832009-02-13T14:47:00.000-05:002009-02-13T14:47:00.000-05:00A. J. BLOOM of Davis Ca has an interesting hypothe...A. J. BLOOM of Davis Ca has an interesting hypothesis linking photorespiration to NO3 assimilation in C3 plants - increased CO2 or decreased O2 levels (therefore more 'effective' Rubisco) leads to a decrease in nitrate assimilation, obviously as nitrogen is one of the most important macronutrients for crop plants reduced nitrogen assimilation is a bad thing for yield in crop plants - if photorespiration is somehow linked to nitrate assimilation then rubisco could be acting as a dual functional enzyme in C3 plants (in C4 plants the same effect was not seen, not that one would expect it to be as C4 rubisco exists in CO2 saturated environment and therefore works near optimal levels)Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-72872481756729715572007-09-08T03:27:00.000-04:002007-09-08T03:27:00.000-04:00art, in my opinion you've hit the nail on the head...art, in my opinion you've hit the nail on the head. What has not been discussed here is that the carboxylation reaction is in fact very complex (consisting of five different partial reactions) and that ALL Rubiscos have the same crucial active site residues and catalytic chemistry. Therefore we might not expect evolution to be able to solve the problem.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-87830595498889728272007-07-14T10:56:00.000-04:002007-07-14T10:56:00.000-04:00A scenario and a question.The scenario: Carboxyla...A scenario and a question.<BR/><BR/>The scenario: Carboxylase activity arose or evolved in a time or under conditions where oxygenase activity was not an issue (very low levels of oxygen, say). The nice "fit" of oxygen in the rubisco active site is a coincidence that factored in later in the evolution of life on earth.<BR/><BR/>The question: Is this an adaptationist rationalization?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-54276721215832527022007-07-13T22:55:00.000-04:002007-07-13T22:55:00.000-04:00You should iron this out with Professor Pulleyblan...You should iron this out with Professor Pulleyblank, because he mentioned an adaptive explanation for the oxygenation reaction. I'm not sure if he's right or wrong, but blatant contradiction between professors is confusing.Alexhttps://www.blogger.com/profile/02590604089043425452noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-32397038520168155692007-07-13T15:36:00.000-04:002007-07-13T15:36:00.000-04:00Nick Matzke asks,In other words, why does everyone...Nick Matzke asks,<BR/><BR/><I>In other words, why does everyone think it should be possible to do very much better with this very difficult chemical process?</I><BR/><BR/>Because there are many other kinds of reactions where CO2 is fixed and O2 does not act as a significant competing substrate. <BR/><BR/>What I don't understand is the perspective of the Intelligent Design Creationists. How do they explain such a sloppy enzyme? Couldn't God have done a better job?Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-40849028967438261012007-07-13T11:21:00.000-04:002007-07-13T11:21:00.000-04:00Larry -- I agree about adaptationism here.Here is ...Larry -- I agree about adaptationism here.<BR/><BR/>Here is my question: isn't it true that distinguishing CO2 from O2 is going to be a fundamentally difficult thing to do, chemically speaking, particularly when photosynthesis has sucked CO2 down to 300 ppm and O2 is 210,000 ppm in the atmosphere?<BR/><BR/>In other words, why does everyone think it should be possible to do very much better with this very difficult chemical process?<BR/><BR/>(There might actually be a good reason, I'm just asking.)Nick (Matzke)https://www.blogger.com/profile/17024530213011582673noreply@blogger.com