酶在低溫下會否變性[denatured]?

i was once a AL student studying biology. from my AL knowledge, enzyme denaturation happens when the temperature increase, which provides heat to break intramolecular bonds like ionic bond, disulphide bridge,etc. the higher the temperature, the more heat is provided to overcome the bonding energy. when the active site is destroyed, the enzyme loses its activity, hence denatured. therefore, as long as the bondings exist, the structure of the enzyme will not collapse. nevertheless, low temperature even stablize the bondings, as less heat is provided to overcome the bonding energy.

i think felix's answer is correct in general cases, like inside human body. the situation that pun mentioned is very extreme, like below 0C.

Dear "n",

You asked a good question - after some good thinking.
You are correct that low temperature can cause protein denaturation.
Please see the reference websites below.

http://answers.yahoo.com/question/index?qid=20081021202811AAMmXzv
http://www.lsbu.ac.uk/water/protein2.html

I am afraid felix's reply is inaccurate.

2012-07-05 10:54:56 補充：
I am not sure if it is correct to say the "protein collapse" at low temperature.
Hydrophobic collapse is one hypothesis of cold denaturation of proteins.
It explains some folding/unfolding phenomena.
The damage to the folding of proteins at low temperature involves water molecules (hydration).

2012-07-05 10:55:28 補充：
Jeremy, please note when we talk about the denaturation of proteins, we are talking about the change in their tertiary structure. It may not be necessarily at the active site.

felix's information is partly correct and that's why I said it is inaccurate.

2012-07-05 10:56:04 補充：
Try to key in the term "cold denaturation of proteins" on any internet search engines and there would be a lot of related information prompt up. That is to say proteins could be denatured at low temperature.

2012-07-05 10:56:29 補充：
In an academic journal article, it is stated
"Cold denaturation is a general phenomenon of globular proteins."
(Ref: http://lib.semi.ac.cn:8080/tsh/dzzy/wsqk/selected%20papers/Journal%20of%20Molecular%20Biology/259-805.pdf)

低溫令酶的分子運動下降，
酶與受質相撞機會下降，
這才是令酶活性下降的主因。

你的推理：低溫令酶的分子運動減少亦應令酶的結構塌陷而變性
這並不正確。
酶的本質是蛋白質，由不同的多肽鏈摺疊而成，
而為了維持形狀(維持活性部位)，多肽鏈與多肽鏈之間有不同的鍵合(eg.氫鍵, 離子鍵, 二硫鍵, 厭水性相互作用)。

在過高的溫度下，以上部分鍵合會被破壞，
酶不能維持形狀，即變性，
這才是酶活性下降的主因。

在低溫下，酶沒有改變過它的形狀，
因此，酶由低溫加熱至過熱的期間，
酶活性會有所提升。