Structural and enzymatic properties of 1-aminocyclopropane-1-carboxylate deaminase homologue from Pyrococcus horikoshii.
1-Aminocyclopropane-l-carboxylate deaminase (ACCD) is a pyridoxal 5/-phosphate dependent enzyme that shows deaminase activity toward ACC, a precursor of plant hormone ethylene. ACCD from some soil bacteria has been reported to be able to break the cyclopropane ring of ACC to yield a-ketobutyrate and ammonia. We reported the crystal structure of ACCD from the yeast Hansenula saturnus in the absence/presence of substrate ACC, and proposed its ingenious reaction mechanisms. In order to study the enzyme further, we overexpressed the ACCD homologue protein (phAHP) from the fully decoded hyperthermophilic archearon, Pyrococcus horikoshii OT3. However, phAHP does not show ACCD activity at high temperature as well as at room temperature, though it has significant sequence similarity. Instead of ACCD activity, the GC-MS analysis and enzymatic method show that phAHP has deaminase activity toward L and D-serine. Here, we present the crystal structures of the native and ACC-complexed phAHP. The overall topology of the phAHP structure is very similar to that of ACCD; however, critical differences were observed around the active site. Here, the differences of enzymatic activity between phAHP and ACCD are discussed based on the structural differences of these two proteins. We suggest that the catalytic disagreement between these two enzymes comes from the difference of the residues near the pyridine ring of pyridoxal 5'-phosphate (PLP), not the difference of the catalytic residues themselves. We also propose a condition necessary in the primary sequence to have ACCD activity.
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
Aiko
A
Fujino
Toyouki
T
Ose
Min
M
Yao
Tetsuo
T
Tokiwano
Mamoru
M
Honma
Nobuhisa
N
Watanabe
Isao
I
Tanaka
D000595:Amino Acid Sequence; D001483:Base Sequence; D019755:Carbon-Carbon Lyases / Q000737:chemistry / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D043902:Pyrococcus horikoshii / Q000201:enzymology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D011994:Recombinant Proteins; C033634:1-aminocyclopropane-1-carboxylate deaminase; D019755:Carbon-Carbon Lyases