N-acetyl-l-methionine is a superior protectant of human serum albumin against photo-oxidation and reactive oxygen species compared to N-acetyl-l-tryptophan

• Published in: Biochimica et biophysica acta Vol. 1840; no. 9; pp. 2806 - 2812
• Main Authors: Kouno, Yousuke, Anraku, Makoto, Yamasaki, Keishi, Okayama, Yoshiro, Iohara, Daisuke, Ishima, Yu, Maruyama, Toru, Kragh-Hansen, Ulrich, Hirayama, Fumitoshi, Otagiri, Masaki
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.09.2014
• Subjects: additives; Antioxidant activity; circular dichroism spectroscopy; denaturation; differential scanning calorimetry; enthalpy; Free Radical Scavengers - chemistry; Human serum albumin; Humans; irradiation; Methionine - analogs & derivatives; Methionine - chemistry; N-Acetyl-l-methionine; N-Acetyl-l-tryptophan; Octanoate; Oxidation-Reduction; pasteurization; Photo-oxidation; Photochemical Processes; photooxidation; polyacrylamide gel electrophoresis; Protein Stability; reactive oxygen species; Reactive Oxygen Species - chemistry; Serum Albumin - chemistry; sodium; spectrophotometers; stabilizers; temperature; toxic substances; Tryptophan - analogs & derivatives; Tryptophan - chemistry; Western blotting; Oct; CD; Human serum albumin; N-Acetyl-l-methionine; N-AcTrp; Photo-oxidation; DSC; Antioxidant activity; HSA; N-Acetyl-l-tryptophan; N-AcMet; Octanoate
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2014.04.014

Sodium octanoate (Oct) and N-acetyl-l-tryptophan (N-AcTrp) are widely used as stabilizers during pasteurization and storage of albumin products. However, exposure to light photo-degrades N-AcTrp with the formation of potentially toxic compounds. Therefore, we have examined the usefulness of N-acetyl-l-methionine (N-AcMet) in comparison with N-AcTrp for long-term stability, including photo stability, of albumin products. Recombinant human serum albumin (rHSA) with and without additives was photo-irradiated for 4weeks. The capability of the different stabilizers to scavenge reactive oxygen species (ROS) was examined by ESR spectrometry. Carbonyl contents were assessed by a spectrophotometric method using fluoresceinamine and Western blotting, whereas the structure of rHSA was examined by SDS-PAGE, far-UV circular dichroism and differential scanning calorimetry. Binding was determined by ultrafiltration. N-AcMet was found to be a superior ROS scavenger both before and after photo-irradiation. The number of carbonyl groups formed was lowest in the presence of N-AcMet. According to SDS-PAGE, N-AcMet stabilizes the monomeric form of rHSA, whereas N-AcTrp induces degradation of rHSA during photo-irradiation. The decrease in α-helical content of rHSA was the smallest in the presence of Oct, without or with N-AcMet. Photo-irradiation did not affect the denaturation temperature or calorimetric enthalpy of rHSA, when N-AcMet was present. The weakly bound N-AcMet is a superior protectant of albumin, because it is a better ROS-protector and structural stabilizer than N-AcTrp, and it is probable and also useful for other protein preparations. N-AcMet is an effective stabilizer of albumin during photo-irradiation, while N-Ac-Trp promotes photo-oxidative damage to albumin. [Display omitted] •N-acetyl-l-methionine can replace N-acetyl-l-tryptophan for albumin products.•N-acetyl-l-methionine acts as a new and safe stabilizer for albumin products.•N-acetyl-l-tryptophan has low photo-stability and could give rise to toxic compounds.•N-acetyl-l-methionine was found to be a superior ROS scavenger.•N-acetyl-l-tryptophan induces degradation of albumin during photo-irradiation.