β alanine

Anserine (Figure 1), carnosine, L-histidine, 1-methyL-histidine, β-alanine, phenylephrine, acetonitrile, trifluoroacetic acid, trichloroacetic acid, aminoadipic acid, triethylamine and phenyl isothiocyanate were purchased from Fujifilm Wako Pure Chemical (Osaka, Japan). Hydrophilic nylon syringe filters (0.45 μm) were purchased from Hamach Scientific (Xi’an, China). Anserine, carnosine, L-histidine, 1-methyL-histidine and β-alanine were dissolved in distilled water and filtered before used. Marine Active^® was provided by Yaizu Suisankagaku Industry (Shizuoka, Japan) and stored at 4 °C. Marine Active^® contains 38% anserine, 26.2% L-histidine, 3.4% carnosine and 32.4% others.

The Escherichia coli JM109 competent cells, PrimeSTAR HS DNA polymerase, EmeraldAmp MAX PCR Master Mix, In-Fusion HD cloning kit, and NcoI were purchased from Takara Bio, Inc. (Shiga, Japan). The pQE-60 plasmid was obtained from Qiagen GmbH (Hilden, Germany). Poly(R)-3-hydroxybutyric acid, ( ±)3-hydroxybutyric acid (3HB) sodium salt and L-methionine sulfone were purchased from Sigma-Aldrich, Inc. (St. Louis, MO, USA). Acetone, sulfuric acid, methanol, sodium D-pantothenate, β-alanine, ampicillin sodium salt (Ap), chloramphenicol (Cm), isopropyl β-D-thiogalactopyranoside (IPTG), ethanol for HPLC, and chloroform for HPLC were purchased from FUJIFILM Wako Pure Chemical Corporation (Osaka, Japan). Oligonucleotides for PCR and DNA sequencing were purchased from Eurofins Genomics K.K. (Tokyo, Japan). PIPES sesquisogium and D-camphor-10-sulfonic acid were purchased from Dojindo Laboratories Co., Ltd. (Kumamoto, Japan) and Nacalai Tesque, Inc. (Kyoto, Japan), respectively. Amicon Ultra-0.5 Centrifugal Filter Units (3 kDa) were obtained from Merck KGaA (Darmstadt, Germany). All other chemicals were of reagent grade.