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February 2008 In this issue ………
Enzymes				- how they work - sources of enzymes - monitoring enzyme reactions - safety considerations - troubleshooting enzyme reactions - choosing a suitable enzyme experiment - enzymes available from Southern Biological - modeling enzyme reactions
Also				- Ferro Fluid, really weird stuff - Specials – Neo/SLIDE titles at only $15.00+GST - Resources – Check out these great links - Contact your association - Coming events – Catch up on CONASTA - Did you know? Ethanol as a biofuel
How Enzymes Work top of page
Essentially, enzymes lower the activation energy of a biochemical reaction, thus increasing the rate at which it occurs. There are various mechanisms by which they can do this, but the common factor is for the enzyme to form a complex with the substrate by binding to it in some way. In this situation, the reaction proceeds quickly and the reaction products are released, thus freeing the enzyme to bind to another unit of substrate for the process to be repeated.
Sources of Enzymes top of page
It is tempting to think of enzymes as discreet chemical entities with constant chemical properties. However, this can be misleading because enzymes are proteins that can vary in structure and the way they fulfil their catalytic purpose. For example, amylase is often described as an enzyme that breaks starch down into sugars. However, there are many different types of amylase in the various animals and micro-organisms that metabolise starch. They are collectively referred to as amylase because of their common purpose – the breakdown of starch – but they can be significantly different biochemicals. Most commercial enzymes these days are derived from bacterial or fungal cultures that can be grown in large bioreactors to maximize the yield. Rather than purifying the product to a high degree, commercial enzymes are usually mixed with an inert diluent to minimize variation between batches. The efficacy of enzymes is usually described in terms of their “activity”, or the quantity of substrate they can convert in a given time. This is more meaningful than “concentration” when comparing two similar enzymes. For example, it makes no sense to describe two types of amylase at the same concentration as being equivalent if one is ten times more active than the other.
Monitoring Enzyme Reactions top of page
Reactions involving enzymes can be monitored by following the disappearance of the substrate, the appearance of the reaction products, or both simultaneously. Students can take spot readings then tabulate and graph the results. Where possible, using a datalogger allows direct comparison of the effects of changes in temperature and pH.
Enzyme Safety Considerations top of page
Enzymes are biologically active proteins that can be harmful, so it is prudent to handle all enzymes with care. In particular, avoid inhalation of dust when dealing with enzyme powders, and wear gloves when handling solutions.
Troubleshooting Enzyme Reactions top of page
Like all biochemical reactions, experiments involving enzymes are prone to problems that can arise from many sources. Here are some examples of problems we have seen: Reagents Aged As enzymes age, they are subject to deterioration, especially if they are stored inappropriately. For example, if they have been exposed to light or moisture, or left too long at the wrong temperature. In many cases, the enzyme will still be usable, although some changes to the experimental protocol may be required to accommodate the reduced activity. Incorrect concentrations To get a reaction in a suitable time frame, you should ensure that the concentrations of the enzyme and the substrate are correct. Although enzymes are catalysts and therefore able to react many times, overall reaction rates can be increased by using more enzyme because it allows more substrate molecules to participate at any given time. Incorrect reaction conditions Since enzymes react in a particular “window” framed by temperature and pH, it is important to control these variables. Changing the source Different sources of enzyme or substrate can affect the outcome of enzyme reactions, so carry out a check whenever a new package is opened. Recommendation Always check the enzyme reaction ahead of time to ensure it will work as expected for your students. If necessary, adjust the conditions (concentration, temperature, pH) to get a result in a suitable time frame. Enzyme reactions described in texts tend to generalize, so always allow sufficient time to check the results and make any adjustments that might be necessary for your particular circumstances.
Choosing a suitable enzyme experiment top of page
Rather than simply following the recommendations of a text, take some time to choose the enzyme prac (or pracs) that will suit your class:
	Enzymes that react on proteins (e.g. trypsin, pepsin, protease, and also pancreatin), allow students to see a visible result as the insoluble protein is converted to soluble amino acids. The reaction can be followed visually, or better still, by using a datalogger.
		Click to watch a Quicktime movie of trypsin acting on low fat milk Click to view datalogger results
	Lipase and urease cause a pH change that can be monitored by the changing colour of an indicator, or by using a pH meter or datalogger. Rennet (and junket powder) cause a change in viscosity that is easy to detect. Amylase (clarase) responds well to temperature changes, and amylase (diastase) allows the reaction to be monitored in two ways – loss of starch substrate, and appearance of sugar products.
Enzymes available from Southern Biological top of page
Reliable enzyme reactions are ideal lab activities for students in both chemistry and biology, so take a moment to work out what would suit your students and facilities. Click here to be transferred to our on-line catalogue. Explore and review the full range of enzymes we now offer. For further information and technical advice, please contact us.
Modeling enzyme reactions top of page
To reinforce the principles behind enzyme chemistry, try Enzyme Lab, an interactive program developed in Australia by Newbyte. Product code SW22.30. Click here for details.
Ferro Fluid top of page
This is really weird stuff. It consists of nano-scale magnetic particles that align along the lines of force in a magnetic field. It’s an eye catching way to demonstrate and explain magnetism, nano-technology, colloids, and surface tension. Watch a Quicktime movie of Ferro Fluid reacting to a changing magnetic field. Visit our website for further details.
Specials top of page
We have a number of discounted multimedia products available on our specials list at the moment. Amongst others, you’ll find a large collection of Neo/SLIDE titles. These CD’s present an interesting range of digital micrograph collections that make a useful supplement to many biology topics. Students can manipulate each image on screen, and teachers can create custom presentations and tutorials. These discs are great value at only $15.00+GST each. Click here to view the full specials list.
Resources top of page
Biozone links - a comprehensive list of sites related to science and education. If you haven’t accessed the resources of Biozone before, don’t wait any longer. Australian Chemistry Podcasts - Richard Meagher teaches science at Mt Lawley Senior High School in WA. Check out his collection of audio and video podcasts covering a wide range of Year 12 Chemistry topics. Smithsonian EcoCentre - Use this fantastic resource to find articles, slideshows and videos on topics that affect our relationship with the oceans. About Darwin - Find out everything you ever wanted to know about Charles Darwin on this site maintained by science historian, David Leff.
Get in touch with your association top of page
			ASTA			STATAS
			STAV			SASTA
			STANSW			STA – NT
			SEA – ACT			STAWA
			STAQ
Coming Events top of page
CONASTA, the annual conference of the Australian Science Teachers’ Association, will be held on the campus of Griffith University at the Gold Coast in Queensland from July 6th to 9th. This year’s program will include plenty to interest laboratory technicians as well as teachers. To find out more, visit the CONASTA57 website.
Did you know? Ethanol as a biofuel top of page
Ethanol is being suggested as an environmentally sound biofuel to replace conventional fossil fuels. Ethanol is made by fermenting sugar which can be obtained directly by extraction from cane or beet, or indirectly by breaking down starch. In the US, the main source of starch is corn, but in Australia it is wheat. In each case, there are ethical questions about diverting traditional food sources into fuel, and the energy “payback” is questionable. Research is aimed at finding efficient ways to convert cellulose from plant waste such as stalks, into fermentable sugars that can be used as a source of ethanol. This is akin to the digestion process of herbivores such as cattle that are able to extract energy from cellulose. Isolating suitable enzymes (cellulases) from organisms that can digest cellulose is the basis of much of this work. For example, read about the products being developed by Genencor. For more interesting perspectives on this topic, listen to these short podcasts from Microbe World Radio:
			Bioethanol
			Corn Fever
			Engineering Ethanol
			Cellulosic Ethanol
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