Reactions and Enzymes (2)?

本節(jié)內(nèi)容承接上一部分，主要是對酶的實驗室方法討論（超短預(yù)警）不太明白的或者有錯誤的地方隨時來找UP主喔~ 本部分的參考文獻(xiàn)Essential Cell Biology, 5th ed. Alberts, et al. 2019. 部分內(nèi)容來自khanacademy與維基百科.

封面圖：https://swh-826d.kxcdn.com/wp-content/uploads/2010/07/substrate-enzyme-complex.jpg（有改動）

2d Lab techniques (Michaelis Menten Kinetics)

Substrate to Product

To get information about an enzyme’s activity:

????1.?Mix enzyme & substrate (only varying the [S] in each tube, 這個[ ]表示濃度, [S]即為substrate concentration)

????2.?Measure the velocity (V = amount/second, reaction rate)

Determine the relationship between [S] and V

????Low [S]: not all E bind to S, many free E, not much ES complex. V is slow

????As [S] increases: more ES, V is higher

????????Until most E is ES, V is even higher, but reach highest V even adding more S, because there will be no free E to bind to. V=Vmax at this point

????????As [S] increases, the enzyme becomes more saturated.

Km = [S] needed for V = 1/2 Vmax: how easy is it to saturate the enzyme, how tightly does enzyme bind substrate?

When [S] = Km, the enzyme is half saturated

?

Vmax is related to how fast ES - EP (step 2, see below)

Km is related to how tightly E binds S (step 1, see below)

????????Weak binding, E is less saturated at low [S], Km is large (favors left, S)

????????Tight binding, E is easily saturated at low [S], Km is small (favors right, P)

?

Enzyme Kinetics Experiment Summary:

- Measure: V at various [S]

- Determine:

????Vmax: how fast can the enzyme work when it is saturated with S

????Km: how easy is it to saturate the enzyme

總結(jié)：實驗中記錄反應(yīng)速率與基質(zhì)濃度的關(guān)系并繪制圖像，根據(jù)圖像判斷Vmax以及Km的數(shù)值。Vmax即可達(dá)到的最大反應(yīng)速率，體現(xiàn)了酶的最大飽和速率；Km即達(dá)到一半Vmax時所需的基質(zhì)濃度，體現(xiàn)了酶與基質(zhì)的粘合程度：所需基質(zhì)濃度越低，則意味著較小的基質(zhì)濃度就足以讓酶達(dá)到一半Vmax速率，表明酶更容易與基質(zhì)粘合。