ScienceAsia 32 Supplement 1 (2006): 019-023 |doi: 10.2306/scienceasia1513-1874.2006.32(s1).019
Increased Thermostability and Activity of Chemically
Modified Bromoperoxidase from the Red Alga Gracilaria tenuistipitata
Jirasak Kongkiattikajorna* and Bhinyo Panijpanb
ABSTRACT: Chemical modification of proteins is widely used as a tool for studying localization of individual
amino acids, their participation in the maintenance of the native conformation and for their stabilization.
Amino groups of bromoperoxidase from the red seaweed Gracilaria tenuistipitata Chang & Xia (collected in
Eastern Thailand, at Ban Laem Sok beach in Trad province) were modified with iodoacetamide to change its
structure and to increase its hydrophobicity. The effect of the chemical modification on substrate affinity and
catalytic activity were studied. Chemical modification of the enzyme improved the specific activity up to 5
times. In addition, the chemical modification slightly increased the solvent concentration at which the
enzyme was catalytically active. The thermostabilities of native and modified bromoperoxidase were assayed.
The chemical modification of bromoperoxidase increased its thermostability after incubation at 25oC for
144 h (about 3.3 fold); the modified form retained 20% of its activity after incubation at 45oC for 60 h. The
optimum pH activity is 5.5 for both native and modified forms of the enzyme. The modified enzyme could
tolerate a higher temperature than the native enzyme. This biocatalytic behavior could be attributed to the
increased hydrophobicity of the enzyme. On the other hand, the chemical modification of the enzyme
altered its hydrophobic characteristic and affected the specific activity.
a School of Bioresources and Technology, King Mongkut’ s University Technology Thonburi, Thailand.
b Department of Biochemistry, Faculty of Science, Mahidol University, Thailand.
* Corresponding author, E-mail: firstname.lastname@example.org