Difference between revisions of "Part:BBa J45001"

(→‎Usage and Biology)
 
(6 intermediate revisions by 2 users not shown)
Line 2: Line 2:
 
<partinfo>BBa_J45001 short</partinfo>
 
<partinfo>BBa_J45001 short</partinfo>
  
−
From snapdragon (A. Majus)
+
<partinfo>BBa_J45001</partinfo> encodes SAM salicylic acid carboxyl methyltransferase I derived from ''SAMT'' from ''Antirrhinus majus'' (snapdragon). SAMT catalyzes the conversion of salicylic acid to methyl salicylate.  Methyl salicylate has a wintergreen smell.
  
 
===Usage and Biology===
 
===Usage and Biology===
−
#(GenBank Accession No. AF515284)
+
*The culture medium of ''E. coli'' cells expressing ''SAMT'' contained methyl salicylate (2.1 &mu;g/ml) when the growing medium was supplemented with 5 &mu;g/ml salicylic acid, and methyl benzoate (0.86 &mu;g/ml) when the growing medium was supplemented with 5 &mu;g/ml benzoic acid.
−
#It is a homodimer with subunit molecular mass of about 45 kDA
+
*''E. coli''-expressed SAMT catalyzes the formation of the volatile ester methyl salicylate from salicylic acid with a K<sub>m</sub> (salicylic acid) of 83 and a K<sub>m</sub> (SAM) of 3-4. SAMT can also methylate benzoic acid to form methyl benzoate, but its K<sub>m</sub> value for benzoic acid is 1720 M (much larger). k<sub>cat</sub>/K<sub>m</sub> for salicylic acid is 132 s<sup>-1</sup> M<sup>-1</sup>, and activity with substrate benzoic acid is 45% of the activity with substrate salicylic acid. All other acids yield 0% activity.
−
#On the pET-28a expression vector there is a convenient NdeI site at the initiating ATG codon as well as a BamHI site downstream of the stop codon. Natalia Dudareva is sending the pET-28a vector
+
 
−
#concentration: The culture medium of the E. coli cells expressing this SAMT contained methyl salicylate (2.1 μg/ml) when the growing medium was supplemented with 5 μg/ml salicylic acid. Also, they contained methyl benzoate (0.86 μg/ml) when the growing medium was supplemented with 5 μg/ml benzoic acid
+
−
#pH optimum from 7.0 to 7.5, but the expressed recombinant SAMT enzyme still has 80%-90& maximum activity in pH from 5.0 to 8.0. The enzyme was active in both Tris- and phosphate-citrate-based buffers, although phosphate was 20% lower. Incubation for 30 mins at 42 C had no effect on activity, showing that this SAMT has the broadest temperature stability of this family of enzymes. Also, SAMT activity was not affected by the presence of 5mM Mg2+, K+, NH4+, or Ca2+ in assay reaction.  
+
−
#It does not require any metal ions as cofactors
+
−
#Fe2+ and Cu2+ have a strong inhibitory effect
+
−
#Because we are receiving the gene for this enzyme on a pET-28a plamid, the gene is transcribed by T7 polymerase rather than by E. coli polymerase. T7 polymerase is much faster than E. coli so we can expect to get very high expression levels.
+
 
<!-- -->
 
<!-- -->
 
<span class='h3bb'>Sequence and Features</span>
 
<span class='h3bb'>Sequence and Features</span>

Latest revision as of 21:44, 9 March 2008

SAM:salicylic acid carboxyl methyltransferase; converts salicylic acid to methyl salicylate (winter

BBa_J45001 encodes SAM salicylic acid carboxyl methyltransferase I derived from SAMT from Antirrhinus majus (snapdragon). SAMT catalyzes the conversion of salicylic acid to methyl salicylate. Methyl salicylate has a wintergreen smell.

Usage and Biology

  • The culture medium of E. coli cells expressing SAMT contained methyl salicylate (2.1 μg/ml) when the growing medium was supplemented with 5 μg/ml salicylic acid, and methyl benzoate (0.86 μg/ml) when the growing medium was supplemented with 5 μg/ml benzoic acid.
  • E. coli-expressed SAMT catalyzes the formation of the volatile ester methyl salicylate from salicylic acid with a Km (salicylic acid) of 83 and a Km (SAM) of 3-4. SAMT can also methylate benzoic acid to form methyl benzoate, but its Km value for benzoic acid is 1720 M (much larger). kcat/Km for salicylic acid is 132 s-1 M-1, and activity with substrate benzoic acid is 45% of the activity with substrate salicylic acid. All other acids yield 0% activity.

Sequence and Features


Assembly Compatibility:
  • 10
    COMPATIBLE WITH RFC[10]
  • 12
    INCOMPATIBLE WITH RFC[12]
    Illegal NheI site found at 577
  • 21
    INCOMPATIBLE WITH RFC[21]
    Illegal XhoI site found at 901
  • 23
    COMPATIBLE WITH RFC[23]
  • 25
    INCOMPATIBLE WITH RFC[25]
    Illegal NgoMIV site found at 421
    Illegal NgoMIV site found at 425
  • 1000
    INCOMPATIBLE WITH RFC[1000]
    Illegal SapI site found at 471
    Illegal SapI.rc site found at 75

Functional Parameters

ec_numnone
keggnone
proteinSAMT
swissproQ8H6N2