Tyrosine decarboxylase -- characteristics of tyrosine decarboxylase of Streptococcus faecalis in Worthington

Tyrosine decarboxylase catalyzes the removal of carboxyl groups from tyrosine , Tyramine and carbon dioxide are produced .

5'- Pyridoxal phosphate is an essential coenzyme . By using vitamins  B6  Lack of coenzyme removal prepared by cells growing on the medium  (TYDAPO), Pyridoxal phosphate can be determined . See  Umbreit wait forsomeone .(1945)  and  Gunsalus  And Smith  (1957). The decarboxylation of radiolabeled tyrosine allows the determination of a smaller amount of pyridoxal phosphate （Maruyama  and  Coursin 1968;Sundaresan  and  Coursin 1970）. Acetone dried cells are used as a relatively simple source of aposylase extraction and purification .

Holoenzyme can be used to determine tyrosine by manometry or colorimetry 、 Phenylalanine and dihydroxyphenylalanine .Tashian (1957)  A method for the determination of tyrosine in urine based on this principle is reported . Plasma phenylalanine can also be measured with this enzyme . The original method was  Udenfriend  and  Cooper (1953)  describe , The modification has been made by  Hsia (1959)  and  Knox  and  Messinger (1958)  publish .Poisner (1960)  Use  Hsia  The serum phenylalanine level of schizophrenic patients was measured , The results were significantly higher than normal .

Boeker  and  Snell (1972)  Amino acid decarboxylase is reviewed . See also  Snell  and  DiMari (1970).

AI Meijie Worthington dung Characteristics of Streptococcus tyrosine decarboxylase ：

The best  pH  value ：5.5（Boeker  and  Snell 1972）.

Specificity ：L- The rate of action of phenylalanine and dihydroxyphenylalanine  L- Tyrosine is much slower .

Inhibitors ： Heavy metals （Ag +、Cu 2+、Fe 2+、Fe 3+、Pb 2+）KCN、NHOH、N 2 H 4 and SO 4=.

Stabilizers ： glycerol  10-25%、 Mercaptoethanol  (5 mM)  and  L- Tyrosine  (0.5 mM) (Chabner and Livingston 1970; Sundaresan and Coursin 1970).

 

 

AI Meijie Worthington Tyrosine decarboxylase Determination method ：

The determination method used here is based on  Gunsalus  and  Smith  Determination of （ Enzymatic methods ,III,（Colowick, S.  and  Kaplan, N.  edit ）,Academic Press, NY, 963, 1957）. Under specified conditions , A unit in  37°C  and  pH 5.5  Every minute from  L- Tyrosine produce  1  Micromore  CO 2 .

Reagents ：

1.0.8 M  Sodium acetate ,pH 5.5

2.0.074 M  Sodium acetate ,pH 5.5

3.0.0065 M L- Tyrosine in reagent grade water . Stir and heat until  80°C  dissolution . Balance to  37°C.（ If the solution cools , Crystals may form ）.

enzyme ：

Dissolve the enzyme in  0.074 M  Sodium acetate ,pH 5.5  in , The concentration is  2 mg/ml. Mix well immediately before taking out the aliquot .

Program ：

Move the following pipettes into  Warburg  In the main hole of the flask ：

0.8 M  Sodium acetate ,pH 5.5 0.2  ml

0.0065 M L- Tyrosine ,37°C 2.3  ml

Remove  0.5 ml  The enzyme suspension is put into the side arm of the flask . Include an enzyme free flask as blank , A flask without enzyme is used as blank , One with  3.0 ml  The flask of reagent grade water acts as a thermobarometer . Connect the flask to the pressure gauge . Balance  10  Minutes later , Turn off the pressure gauge , Pour and mix substrates , Then change the flask in the bath .

Make sure to take about  5  Minutes interval release  30  Minutes of  CO 2 Micromolar number . Draw the released micromolars  CO 2 Relationship with reaction time , And determine the micro moles released per minute from the linear part of the curve .

Worthington Core enzyme ： Include ： Collagenase , Deoxyribonuclease I, Elastase , Papain , Ribonuclease , Trypsin, etc .