菠萝蛋白酶监测方法
Data Sheet - Bromelain恒星英语学习网
Source:
英语文章在线翻译Stem of pineapple (Ananas comosus (L.) MERR.)
Systematic name:
Peptidyl peptide hydrola; EC 3.4.22.32
Other names:
Bromelin, Anana.
CAS-No.
37189-34-7erbitux
E.C.-No.
3.4.22.32
EG-Indexnummer
647-005-00-X
Occurrence
nurry rhymeBromelain is the collective name for proteolytic enzymes found in various members of the family Bromeliaceae. Bromelain from the pineapple (Ananas comosus) is the most studied. The highest enzyme concentration occurs in the lower portion of mature pineapple plant stems, appreciable quantities are also prent in fruits and leaves.
Characteristics
美国奢侈品管理专业Specificity: Two forms (A and B) of Bromelain with similar specificity have been isolated from pineapple stem (1). Bromelain hydrolyzes proteins, peptides, amides and esters of amino acids and peptides; preferential cleavage site is the carbonyl end of lysine, alanine,
tyrosine and glycine (1,2). For relative activities on a number of amino acid substrates e Barman (3). The following side activities can be detected in Bromelain preparations: amyla, phosphata, peroxida, the latter being very labile upon storage.
Effectors:pretending Bromelain is a thiol proteina, i.e. it contains in the active centre a highly reactive cysteine which is esntial for catalysis. Therefore, the enzyme can be activated by reducing compounds, e.g. cysteine, 2-mercaptoethanol, dithiothreitol, KCN (4). On the other hand, Bromelain is irreversibly inhibited by alkylating agents such as N-ethylmaleimide (NEM), iodoacetic acid and 1,3-dibromoacetone (4). Reversible inhibition is caud by inorganic Hg ion, organic Hg compounds and tetrathionate (4).
Catalytic optima: The optimum pH for catalytic activity depends on the nature of substrate, type and concentration of buffer and the prence or abnce of a reducing agent. The optimum pH range is about 4.5-7.5. The optimum temperature is 35-45 °C (5), the maximum operating temperature for industrial application (reaction time ≤4h) is 50 °C (2).
接受英文
Stability: Bromelain is stable at pH 3-6 and at temperatures up to 60 °C (5). Bromelain powder can be stored originally packed and tightly clod up to two years at < 8 °C without loss of activity. Upon opening the activity gradually decreas, unless the enzyme is immediately mixed with diluent (lacto) which prevents the protein from lf-inactivation. Activity loss caud by unproper storage or preparation conditions can be abolished to an appreciable extent by the addition of cysteine.
Solubility: Bromelain powder is partly soluble in water, insoluble in most organic solvents.
Molecular weight:qb是什么意思 33,200 daltons.
Composition: Bromelain is a glycoprotein constituted of one single polypeptide chain with 1 glycan per molecule. The number of amino acids per molecule is not yet unequivocally established. The NH2-terminal amino acid is valine, the COOH-terminal is glycine.
Isoelectric point: 9.55
Spectral data: E280 (1%, 1cm) = 20.1.
Assay
The method described here is the one given by Lauwers and Scharpé (4).
大学英语四级作文模板Principle
Bromelain hydrolyzes cain into small peptides, which cannot be precipitated with a specific reagent. Thus, after incubation (10 min at 35 °C) undigested cain is removed and the amount of peptides remaining in solution is determined spectrophotometrically at 275 nm.
Unit definition
1 FIP unit of Bromelain is the amount of enzyme that hydrolyzes cain under the standard conditions into not acid-precipitable peptides at an initial rate such that there is liberated per minute an amount of peptides which gives the same absorbance at 275 nm as 1 °mole tyrosine.
Reagents
1. Tris-buffer:有过之无不及 0.05 M tris/HCl pH 7.15. Dissolve 6.06 g tris (= tris-(hydroxymethyl)aminomethane) in 600 ml distilled water. Adjust with 1 N HCl at 25 °C to pH 7.15 and add water to a final volume of 1000 ml. At 35 °C the pH must be 7.00.
2. Substrate activation solution: 80 mM cysteine, 10 mM EDTA in Tris-buffer (A). Dissolve 242 mg cysteine and 93 mg EDTA x 2H2O in Tris-buffer (A), adjust to pH 7.15 and fill up to 25 ml with Tris-buffer (A). Prepare fresh daily.
3. Substrate solution: Add 2.5 g cain (e.g. cain for biochemistry, Merck 2242, Merck, Darmstadt, F.R.G.; FIP controlled) to 10 ml distilled water, mix, add 15 ml 0.1 N NaOH and mix thoroughly with a magnetic stirrer for 30 min at 35 °C until all cain is dissolved. Then add 50 ml of Tris-buffer (A) and 10 ml of substrate activation solution (B), adjust pH to 7.15 at 25 °C and make up to 100 ml with Tris-buffer (A). Prepare fresh daily.
4. Enzyme activation solution: 5 mM cysteine, 1 mM EDTA, 10 mM KCl in tris buffer (A).
Dissolve 60.5 mg cysteine, 37.2 mg EDTA x 2H2O and 74.6 mg KCl in Tris-buffer (A), adjust to pH 7.15 and make up to 100 ml with Tris-buffer (A). Prepare fresh daily.
