- Teks
- Sejarah
water-immiscible organic solvents a
water-immiscible organic solvents as in the dry powder, but the half-life of dilute solutions is very short [64]. Subtilisin crystals
placed in acetonitrile have the same crystal structure as does subtilisin crystallized from aqueous solutions [41]. Enzymes do not
turn inside-out when placed in immiscible organic solvents.
The stability and catalytic activity of enzymes in water/water-miscible organic solvent systems are different from those in waterimmiscible
organic solvent systems. Kang et al. [55–57] showed that protease-catalyzed hydrolysis of casein, in either 5%
ethanol/95%
aqueous buffer or 5% acetonitrile/95% aqueous buffer systems, caused an increase in
K
m,
a decrease in
V
max,
and
a
decrease in stability (determined by circular dichroism and differential scanning calorimetry methods) compared to controls in
aqueous
buffer only. It is well known that protic solvents, such as alcohols and amines, compete with water in hydrolytic enzyme
reactions
[5, 9].
7.5.6 Why Enzymes are Effective Catalysts
Enzymes are very effective catalysts as indicated by their ability to lower the activation energy,
E
a, of reactions (Table 2). This
results in larger values of
n
o. But these facts provide no indication of how the enzymes achieve such “magic.” Be assured that
enzymes act by the same principles of all chemical reactions. They just do it better [67].
Listed in Table 11 are the factors that account for the catalytic efficiency of enzymes. Not all enzymes use all possibilities listed,
but all enzymes do bind substrates stereospecifically into the active site where essential groups (side chain of specific amino acids
or required cofactors) perform from the reaction chemistry either by general acid-general base or nucleophilic-electrophilic
processes. It is apparent that the most impressive enhancement of the rate is due to formation of the enzyme-substrate complex,
where the rate enhancement is on the order of 10
4
for a two-substrate reaction, 10
9
for a three-substrate reaction, and 10
(or
more) for a four-substrate reaction.
The seven factors listed in Table 11 can account for 10
18
to 10
36
rate enhancements, if all
15
placed in acetonitrile have the same crystal structure as does subtilisin crystallized from aqueous solutions [41]. Enzymes do not
turn inside-out when placed in immiscible organic solvents.
The stability and catalytic activity of enzymes in water/water-miscible organic solvent systems are different from those in waterimmiscible
organic solvent systems. Kang et al. [55–57] showed that protease-catalyzed hydrolysis of casein, in either 5%
ethanol/95%
aqueous buffer or 5% acetonitrile/95% aqueous buffer systems, caused an increase in
K
m,
a decrease in
V
max,
and
a
decrease in stability (determined by circular dichroism and differential scanning calorimetry methods) compared to controls in
aqueous
buffer only. It is well known that protic solvents, such as alcohols and amines, compete with water in hydrolytic enzyme
reactions
[5, 9].
7.5.6 Why Enzymes are Effective Catalysts
Enzymes are very effective catalysts as indicated by their ability to lower the activation energy,
E
a, of reactions (Table 2). This
results in larger values of
n
o. But these facts provide no indication of how the enzymes achieve such “magic.” Be assured that
enzymes act by the same principles of all chemical reactions. They just do it better [67].
Listed in Table 11 are the factors that account for the catalytic efficiency of enzymes. Not all enzymes use all possibilities listed,
but all enzymes do bind substrates stereospecifically into the active site where essential groups (side chain of specific amino acids
or required cofactors) perform from the reaction chemistry either by general acid-general base or nucleophilic-electrophilic
processes. It is apparent that the most impressive enhancement of the rate is due to formation of the enzyme-substrate complex,
where the rate enhancement is on the order of 10
4
for a two-substrate reaction, 10
9
for a three-substrate reaction, and 10
(or
more) for a four-substrate reaction.
The seven factors listed in Table 11 can account for 10
18
to 10
36
rate enhancements, if all
15
0/5000
water-immiscible organic solvents as in the dry powder, but the half-life of dilute solutions is very short [64]. Subtilisin crystals
placed in acetonitrile have the same crystal structure as does subtilisin crystallized from aqueous solutions [41]. Enzymes do not
turn inside-out when placed in immiscible organic solvents.
The stability and catalytic activity of enzymes in water/water-miscible organic solvent systems are different from those in waterimmiscible
organic solvent systems. Kang et al. [55–57] showed that protease-catalyzed hydrolysis of casein, in either 5%
ethanol/95%
aqueous buffer or 5% acetonitrile/95% aqueous buffer systems, caused an increase in
K
m,
a decrease in
V
max,
and
a
decrease in stability (determined by circular dichroism and differential scanning calorimetry methods) compared to controls in
aqueous
buffer only. It is well known that protic solvents, such as alcohols and amines, compete with water in hydrolytic enzyme
reactions
[5, 9].
7.5.6 Why Enzymes are Effective Catalysts
Enzymes are very effective catalysts as indicated by their ability to lower the activation energy,
E
a, of reactions (Table 2). This
results in larger values of
n
o. But these facts provide no indication of how the enzymes achieve such “magic.” Be assured that
enzymes act by the same principles of all chemical reactions. They just do it better [67].
Listed in Table 11 are the factors that account for the catalytic efficiency of enzymes. Not all enzymes use all possibilities listed,
but all enzymes do bind substrates stereospecifically into the active site where essential groups (side chain of specific amino acids
or required cofactors) perform from the reaction chemistry either by general acid-general base or nucleophilic-electrophilic
processes. It is apparent that the most impressive enhancement of the rate is due to formation of the enzyme-substrate complex,
where the rate enhancement is on the order of 10
4
for a two-substrate reaction, 10
9
for a three-substrate reaction, and 10
(or
more) for a four-substrate reaction.
The seven factors listed in Table 11 can account for 10
18
to 10
36
rate enhancements, if all
15
placed in acetonitrile have the same crystal structure as does subtilisin crystallized from aqueous solutions [41]. Enzymes do not
turn inside-out when placed in immiscible organic solvents.
The stability and catalytic activity of enzymes in water/water-miscible organic solvent systems are different from those in waterimmiscible
organic solvent systems. Kang et al. [55–57] showed that protease-catalyzed hydrolysis of casein, in either 5%
ethanol/95%
aqueous buffer or 5% acetonitrile/95% aqueous buffer systems, caused an increase in
K
m,
a decrease in
V
max,
and
a
decrease in stability (determined by circular dichroism and differential scanning calorimetry methods) compared to controls in
aqueous
buffer only. It is well known that protic solvents, such as alcohols and amines, compete with water in hydrolytic enzyme
reactions
[5, 9].
7.5.6 Why Enzymes are Effective Catalysts
Enzymes are very effective catalysts as indicated by their ability to lower the activation energy,
E
a, of reactions (Table 2). This
results in larger values of
n
o. But these facts provide no indication of how the enzymes achieve such “magic.” Be assured that
enzymes act by the same principles of all chemical reactions. They just do it better [67].
Listed in Table 11 are the factors that account for the catalytic efficiency of enzymes. Not all enzymes use all possibilities listed,
but all enzymes do bind substrates stereospecifically into the active site where essential groups (side chain of specific amino acids
or required cofactors) perform from the reaction chemistry either by general acid-general base or nucleophilic-electrophilic
processes. It is apparent that the most impressive enhancement of the rate is due to formation of the enzyme-substrate complex,
where the rate enhancement is on the order of 10
4
for a two-substrate reaction, 10
9
for a three-substrate reaction, and 10
(or
more) for a four-substrate reaction.
The seven factors listed in Table 11 can account for 10
18
to 10
36
rate enhancements, if all
15
Sedang diterjemahkan, harap tunggu..
pelarut organik tak larut air seperti pada bubuk kering, tapi paruh larutan encer sangat singkat [64]. Kristal Subtilisin
ditempatkan dalam asetonitril memiliki struktur kristal yang sama seperti halnya Subtilisin mengkristal dari larutan air [41]. Enzim tidak
berubah dalam keluar ketika ditempatkan dalam pelarut organik bercampur.
Stabilitas dan aktivitas katalitik enzim dalam air / sistem pelarut organik larut dalam air berbeda dengan di waterimmiscible
sistem pelarut organik. Kang et al. [55-57] menunjukkan bahwa protease-katalis hidrolisis kasein, baik 5%
ethanol / 95%
penyangga berair atau 5% sistem asetonitril / 95% penyangga air, menyebabkan peningkatan
K
m,
penurunan
V
max,
dan
sebuah
penurunan stabilitas (ditentukan oleh dichroism melingkar dan metode kalorimetri pemindaian diferensial) dibandingkan dengan kontrol dalam
air
penyangga saja. Hal ini juga diketahui bahwa pelarut protik seperti alkohol dan amina, bersaing dengan air dalam enzim hidrolitik
reaksi
[5, 9].
7.5.6 Mengapa Enzim adalah Katalis Efektif
Enzim adalah katalis yang sangat efektif seperti yang ditunjukkan oleh kemampuan mereka untuk menurunkan energi aktivasi ,
E
a, reaksi (Tabel 2). Hal ini
menyebabkan nilai-nilai yang lebih besar dari
n
o. Tapi fakta ini tidak memberikan indikasi bagaimana enzim mencapai seperti "magic." Yakinlah bahwa
enzim bertindak dengan prinsip yang sama dari semua reaksi kimia. Mereka hanya melakukannya dengan lebih baik [67].
Tercantum dalam Tabel 11 adalah faktor-faktor yang menjelaskan efisiensi katalitik enzim. Tidak semua enzim menggunakan semua kemungkinan yang terdaftar,
tapi semua enzim yang mengikat substrat stereospecifically ke situs aktif di mana penting kelompok (rantai samping asam amino tertentu
atau kofaktor yang diperlukan) melakukan dari kimia reaksi baik oleh umum asam basa-umum atau nukleofilik-elektrofilik
proses . Hal ini jelas bahwa peningkatan yang paling mengesankan dari angka ini karena pembentukan kompleks enzim-substrat,
dimana peningkatan tingkat adalah di urutan 10
4
untuk reaksi dua-substrat, 10
9
untuk reaksi tiga-substrat, dan 10
(atau
lebih) untuk reaksi empat substrat.
Tujuh faktor yang tercantum dalam Tabel 11 dapat menjelaskan 10
18
10
36
tambahan tingkat, jika semua
15
ditempatkan dalam asetonitril memiliki struktur kristal yang sama seperti halnya Subtilisin mengkristal dari larutan air [41]. Enzim tidak
berubah dalam keluar ketika ditempatkan dalam pelarut organik bercampur.
Stabilitas dan aktivitas katalitik enzim dalam air / sistem pelarut organik larut dalam air berbeda dengan di waterimmiscible
sistem pelarut organik. Kang et al. [55-57] menunjukkan bahwa protease-katalis hidrolisis kasein, baik 5%
ethanol / 95%
penyangga berair atau 5% sistem asetonitril / 95% penyangga air, menyebabkan peningkatan
K
m,
penurunan
V
max,
dan
sebuah
penurunan stabilitas (ditentukan oleh dichroism melingkar dan metode kalorimetri pemindaian diferensial) dibandingkan dengan kontrol dalam
air
penyangga saja. Hal ini juga diketahui bahwa pelarut protik seperti alkohol dan amina, bersaing dengan air dalam enzim hidrolitik
reaksi
[5, 9].
7.5.6 Mengapa Enzim adalah Katalis Efektif
Enzim adalah katalis yang sangat efektif seperti yang ditunjukkan oleh kemampuan mereka untuk menurunkan energi aktivasi ,
E
a, reaksi (Tabel 2). Hal ini
menyebabkan nilai-nilai yang lebih besar dari
n
o. Tapi fakta ini tidak memberikan indikasi bagaimana enzim mencapai seperti "magic." Yakinlah bahwa
enzim bertindak dengan prinsip yang sama dari semua reaksi kimia. Mereka hanya melakukannya dengan lebih baik [67].
Tercantum dalam Tabel 11 adalah faktor-faktor yang menjelaskan efisiensi katalitik enzim. Tidak semua enzim menggunakan semua kemungkinan yang terdaftar,
tapi semua enzim yang mengikat substrat stereospecifically ke situs aktif di mana penting kelompok (rantai samping asam amino tertentu
atau kofaktor yang diperlukan) melakukan dari kimia reaksi baik oleh umum asam basa-umum atau nukleofilik-elektrofilik
proses . Hal ini jelas bahwa peningkatan yang paling mengesankan dari angka ini karena pembentukan kompleks enzim-substrat,
dimana peningkatan tingkat adalah di urutan 10
4
untuk reaksi dua-substrat, 10
9
untuk reaksi tiga-substrat, dan 10
(atau
lebih) untuk reaksi empat substrat.
Tujuh faktor yang tercantum dalam Tabel 11 dapat menjelaskan 10
18
10
36
tambahan tingkat, jika semua
15
Sedang diterjemahkan, harap tunggu..
Bahasa lainnya
Dukungan alat penerjemahan: Afrikans, Albania, Amhara, Arab, Armenia, Azerbaijan, Bahasa Indonesia, Basque, Belanda, Belarussia, Bengali, Bosnia, Bulgaria, Burma, Cebuano, Ceko, Chichewa, China, Cina Tradisional, Denmark, Deteksi bahasa, Esperanto, Estonia, Farsi, Finlandia, Frisia, Gaelig, Gaelik Skotlandia, Galisia, Georgia, Gujarati, Hausa, Hawaii, Hindi, Hmong, Ibrani, Igbo, Inggris, Islan, Italia, Jawa, Jepang, Jerman, Kannada, Katala, Kazak, Khmer, Kinyarwanda, Kirghiz, Klingon, Korea, Korsika, Kreol Haiti, Kroat, Kurdi, Laos, Latin, Latvia, Lituania, Luksemburg, Magyar, Makedonia, Malagasi, Malayalam, Malta, Maori, Marathi, Melayu, Mongol, Nepal, Norsk, Odia (Oriya), Pashto, Polandia, Portugis, Prancis, Punjabi, Rumania, Rusia, Samoa, Serb, Sesotho, Shona, Sindhi, Sinhala, Slovakia, Slovenia, Somali, Spanyol, Sunda, Swahili, Swensk, Tagalog, Tajik, Tamil, Tatar, Telugu, Thai, Turki, Turkmen, Ukraina, Urdu, Uyghur, Uzbek, Vietnam, Wales, Xhosa, Yiddi, Yoruba, Yunani, Zulu, Bahasa terjemahan.
- I mean that you have answered in the tic
- Your current address
- changes in substrate(s) and products(s)
- FeedbackMust follow behavior closely to
- changes in substrate(s) and products(s)
- Het privaatrecht regelt overeenkomsten t
- I mean that you have answered in the tic
- Your permanent address
- I mean that you have answered in the tic
- memories of the pastpast memories
- 7.4.2 Steady-State RatesThe velocity of
- The word "it" refers to
- memories of the pastpast memories
- The second method used to determine whic
- mematahkan
- Your current email address
- Inhibitors are substances which reduce e
- missing someone
- state whered[E.S]/dt =-d[E.S]/dt over th
- De partijen
- never go back
- Aneurysm
- 7.4 Rates of Enzyme-Catalyzed Reactions7
- kenangan masa lalu
