The growth-inhibitory effect of 23 carbohydrate monoesters synthesized by lipases and proteases were assayed to obtain antibacterial agents that suppress the cell growth of Streptococcus mutans. Among the carbohydrate esters synthesized, galactose and fructose laurates showed the highest growth-inhibitory effect, while the other analogs of hexose laurates showed no antibacterial activity, indicating that configuration of the hydroxyl group in carbohydrate moiety markedly affects the antibacterial activity. The cell growth of S. mutans was suppressed by fructose laurates even in the presence of sucrose. Thus, enzymatic synthesis of carbohydrate esters with different core structures has great potential for developing antibacterial agents applicable to food additives.

Lipid peroxidation by managanese peroxidase (MnP) is reported to decompose recalcitrant polycyclic aromatic hydrocabon (PAH) and nonphenolic lignin models. To elucidate the oxidative process, linoleic acid and 13(S)-hydroperoxy-9Z,11E-octadecadienoic acid [13(S)-HPODE] were reacted with MnPs from Ceriporiopsis subvermispora and Bjerkandera adusta and the free radicals produced were analyzed by ESR. When the MnPs were reacted with 13(S)-HPODE in the presence of Mn(II), H 2 O 2 and tert-nitrosobutane (t-NB), the ESR spectrum contained a sharp triplet of acyl radical (a N 0.81 mT). Formation of acyl radical was also observed in the reactions of Mn(III)-tartrate with 13(S)-HPODE and with linoleic acid, but the latter reaction occurred explosively after an induction period of around 30 min. Reactions of MnP with linoleic acid in the presence of Mn(II), H 2 O 2 and t-NB gave no spin adducts while addition of t-NB after preincubation of linoleic acid with MnP/Mn(II)/H 2 O 2 for 2 h gave spin adducts of carbon-centered (a N 1.53 mT, a H 0.21 mT) and acyl (a N 0.81 mT) radicals. In contrast to linoleic acid, methyl linoleate and oleic acid were not peroxidized by MnP and chelated Mn(III) within a few hours, indicating that structures containing both the 1,4-pentadienyl moiety and a free carboxyl group are necessary for inducing the peroxidation in a short reaction time. These results indicate that MnP-dependent lipid peroxidation is not initiated by direct abstraction of hydrogen from the bis-allylic position during turnover but proceeds by a Mn(III)-dependent hydrogen abstraction from enols and subsequent propagation reactions involving the formation of acyl radical from lipid hydroperoxide. This finding expands the role of chelated Mn(III) from a phenol oxidant to a strong generator of free radicals from lipids and lipid hydroperoxides in lignin biodegradation.

Lipid peroxidation by managanese peroxidase (MnP) is reported to decompose recalcitrant polycyclic aromatic hydrocabon (PAH) and nonphenolic lignin models. To elucidate the oxidative process, linoleic acid and 13(S)-hydroperoxy-9Z,11E-octadecadienoic acid [13(S)-HPODE] were reacted with MnPs from Ceriporiopsis subvermispora and Bjerkandera adusta and the free radicals produced were analyzed by ESR. When the MnPs were reacted with 13(S)-HPODE in the presence of Mn(II), H 2 O 2 and tert-nitrosobutane (t-NB), the ESR spectrum contained a sharp triplet of acyl radical (a N 0.81 mT). Formation of acyl radical was also observed in the reactions of Mn(III)-tartrate with 13(S)-HPODE and with linoleic acid, but the latter reaction occurred explosively after an induction period of around 30 min. Reactions of MnP with linoleic acid in the presence of Mn(II), H 2 O 2 and t-NB gave no spin adducts while addition of t-NB after preincubation of linoleic acid with MnP/Mn(II)/H 2 O 2 for 2 h gave spin adducts of carbon-centered (a N 1.53 mT, a H 0.21 mT) and acyl (a N 0.81 mT) radicals. In contrast to linoleic acid, methyl linoleate and oleic acid were not peroxidized by MnP and chelated Mn(III) within a few hours, indicating that structures containing both the 1,4-pentadienyl moiety and a free carboxyl group are necessary for inducing the peroxidation in a short reaction time. These results indicate that MnP-dependent lipid peroxidation is not initiated by direct abstraction of hydrogen from the bis-allylic position during turnover but proceeds by a Mn(III)-dependent hydrogen abstraction from enols and subsequent propagation reactions involving the formation of acyl radical from lipid hydroperoxide. This finding expands the role of chelated Mn(III) from a phenol oxidant to a strong generator of free radicals from lipids and lipid hydroperoxides in lignin biodegradation.