Sandbox Reserved 655: Difference between revisions

<Structure load='3vdh' size='500' frame='true' align='right' caption='Beta-1,4-Endoglucanase' scene='Insert optional scene name here' />

[[Image:3vdh_bio_r_500.jpg | thumb]]

In the past 20 years, researchers have found that endoglucanases cannot break down polysaccharides efficiently without the help of non-catalytic carbohydrate-binding modules. Thus, the 59kDa endoglucanase is mostly found in the form of a complex that is made up of two to three separate domains. The main domain contains the large, globular catalytic domain which expresses the active site. The catalytic module of members of GH family 9 shows an (alpha/alpha)6-barrel structure. The 12 alpha-helices display an alternating connection pattern between outer and inner helices, as is common in (alpha/alpha)6-barrel structures (Parsiegla et al., 1998). The barrel is formed by the parallel inner helices 2, 4, 6, 8, 10 and 12. Besides the 12 alpha-helices, the catalytic module of Aa_Cel9A shows two antiparallel beta-strands and three short alpha-helices which are structurally conserved throughout the family 9 cellulases.A loop of the protein chain forms a tunnel that encloses the <scene name='Sandbox_Reserved_655/Active_site/1'>active site</scene>.  

[[Image:Active site.jpg | thumb]]

The overall shape of the complex looks like a tadpole, with the A and B blocks forming the extended tail and the catalytic domain forming the head (Pilz, et al., 1990).  

Methods for Purification:

Methods for Solving the Structure:

== '''Mechanism''' ==

[[Image:Endoglucanase Mechanism.jpeg]]

Cellulases represent the third largest class of industrial enzymes worldwide because of their use in cotton processing, paper recycling, as detergent enzymes, in juice extraction, and as animal feed additives. The use of cellulases for the production of renewable fuels from lignocellulosic biomass has the potential to create another large industrial consumer of this class of enzymes (Wilson, 2009).

The growing global demand for energy and the environmental problems caused by the burning of fossil fuels have spurred several efforts to develop renewable alternative fuels (Sticklen, 2008). Global climate change will continue to occur due to the increasing effect of carbon emissions in the atmosphere and political clashes will continue to grow over the control and allocation of these depleting resources, and the costs of these fuels will undoubtedly continue to rise (Merino S.T., and Cherry, J., 2007). One potential approach to producing biofuels is to use the carbohydrate polymers located in tailored crops, such as corn stover and switchgrass, as a source of fermentable sugars ( [Sheehan and Himmel, 1999] and [Simmons et al., 2008]). Cellulose is the main polymer of this biomass and the largest organic carbon reservoir on earth (Festucci-Buselli et al., 2007). Physical and/or chemical pretreatment processes that disrupt the hemicellulose–lignin–cellulose complex in plant cell walls are currently used to make the cellulose accessible to cellulases ( [Sheehan and Himmel, 1999] and [Parsiegla et al., 2008]). In order to make cost-effective biofuels, stable cellulolytic enzymes with high activity in post-pretreatment conditions are essential at an industrial scale of production ( [Wilson, 2009] and [Mahadevan et al., 2008]).The bioconversion process uses enzymes such as endoglucanase to break down cellulose into sugars that can be fermented into ethanol (Figure 6) (Wen, et al., 2009.  Researchers have been looking to engineer microorganisms to withstand the harsh conditions of the process and to produce the necessary enzymes abundantly. It is necessary to understand these enzymes more fully and to improve them via protein engineering so that biomass can be efficiently and inexpensively converted into biofuels.)

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(5) Sticklen, M. B. (2008). Plant genetic engineering for biofuels production: towards affordable cellulosic ethanol Nature, 9 (2008), pp. 433–443.