Biological Evaluation of Antibody-Drug Conjugates Produced by Tag-Free Lipoate Ligase A Modification.

The concept of tag-free protein modification has attracted considerable interest in chemical biology because of its flexible and straightforward reaction process. In 2021, a groundbreaking approach using lipoate ligase A (LplA) for tag-free enzymatic modification of antibodies was unveiled, demonstrating its potential for the generation of precise antibody conjugates. In this study, to further explore LplA-mediated antibody-drug conjugate (ADC) synthesis, we performed initial biological evaluations of ADCs synthesized using LplA. Using the anti-HER2 antibody trastuzumab, we introduced octanoic acid azide using LplA and subsequently obtained an ADC using click chemistry with the drug DBCO-VC-PAB-MMAE. The bioactivity of the synthesized anti-HER2-ADC was evaluated using HER2-positive SKBR-3 and HER2-negative MCF7 cells. Its toxicity and selectivity were found to be comparable to those of the FDA-approved Kadcyla. In addition, a stability study involving rat and human plasma demonstrated the stability of the LplA-mediated ADC. Additionally, the affinity for the neonatal Fc receptor (FcRn) was retained after conjugation. These preliminary in vitro evaluations suggested that LplA-derived ADCs can have considerable pharmaceutical potential. Our results can set the stage for further in vivo evaluations and safety assessments. We suggest that the integration of tag-free LplA methods into the production of ADCs can offer a novel and promising approach for biopharmaceutical manufacturing.

Analytical Chemistry of Impurities in Amino Acids Used as Nutrients: Recommendations for Regulatory Risk Management.

Proteinogenic amino acids are natural nutrients ingested daily from standard foods. Commercially manufactured amino acids are added to a wide range of nutritional products, including dietary supplements and regular foods. Currently, the regulatory risk management of amino acids is conducted by means of setting daily maximum limits of intake. However, there have been no reported adverse effects of amino acid overdosing, while impurities in low-quality amino acids have been identified as causative agents in several health hazard events. This paper reviews the analytical chemistry of impurities in amino acids and highlights major variations in the purity of commercial products. Furthermore, it examines the international standards and global regulatory risk assessment of amino acids utilized in dietary supplements and foods, recommending (1) further research on analytical methods that can comprehensively separate impurities in amino acids, and (2) re-focusing on the regulatory risk management of amino acids to the analytical chemistry of impurities.

Association between plasma α-aminobutyric acid and depressive symptoms in older community-dwelling adults in Japan.

AIM: To examine the association between depressive symptoms and plasma amino acid related metaboli in older adults. METHODS: A total of 152 older adults aged ≥65 years, residing in Niigata, Japan, were used for analysis. We evaluated depressive symptoms using the Geriatric Depression Scale-15, which has been validated in older community-dwelling individuals, and used a cut off score of ≥5 to classify participants as having depressive symptoms. We used high-performance liquid chromatography-electrospray ionization mass spectrometry to measure the concentrations of plasma amino acid-related metabolites, and carried out logistic regression analysis to assess the association between depressive symptoms and plasma amino acid-related metabolites. RESULTS: Of the 119 older adults (mean age 76.3 years) included in the analysis, 22 were classified as having depressive symptoms (depressive group). There were no significant differences in physical and cognitive impairments between participants in the depressive and non-depressive groups. The plasma α-aminobutyric acid (AABA) level was significantly lower in the depressive group than in the non-depressive group (P < 0.001). Logistic regression analysis showed the best-fit model, which included AABA, leucine, threonine, hydroxyl proline and histidine levels (area under the receiver operating characteristic curve 0.8346; 95% confidence interval 0.7365-0.9326). In particular, the plasma AABA level was strongly associated with depressive symptoms. CONCLUSIONS: Plasma AABA level is significantly associated with depression symptoms in older community-dwelling adults in Japan. Thus, plasma AABA might serve as a potential marker of depression in older adults aged ≥65 years. Geriatr Gerontol Int 2019; 19: 254-258.

Identification of novel long chain N-acylhomoserine lactones of chain length C20 from the marine phototrophic bacterium Rhodovulum sulfidophilum.

Gram-negative bacterial quorum sensing is mainly regulated by an extracellularly produced N-acylhomoserine lactone (AHL). AHL consists of a lactone ring and an acyl chain, which generally varies from C4 to C18 in length and affords species-specific variety. In this study, we developed an ultra-high performance liquid chromatography tandem mass spectrometry system and detected two kinds of long chain AHLs with chain length C20 from the reverse-phase thin layer chromatography-fractionated cultured supernatant of the marine photosynthetic bacterium Rhodovulum sulfidophilum. By fragmentation search analysis to detect compounds with a homoserine lactone ring moiety for data dependent acquisition, a minor AHL, presumed to be 3-OH-C18-homoserine lactone (HSL), was also found. Among the detected C20-HSLs, 3-OH-C20-HSL was structurally identified and 3-OH-C20:1-HSL was strongly suggested. To our knowledge, this is the first report to show a novel AHL with the longest C20 acyl side chain found to date. ABBREVIATIONS: AGC: automatic gain control; AHL: N-acylhomoserine lactone; CD: cyclodextrin; CID: collision induced dissociation; DDA: data dependent acquisition; EPI: enhanced product ion; FISh: fragment ion search; HCD: high energy collisional dissociation; HSL: homoserine lactone; IT: injection time; LC: liquid chromatography; MS: mass spectrometry; PRM: parallel reaction monitoring; RP: reverse phase; SRM: selected reaction monitoring; TLC: thin layer chromatography; UHPLC: ultra high performance liquid chromatography.

Highly sensitive quantification for human plasma-targeted metabolomics using an amine derivatization reagent.

Amino acids and their related metabolites play important roles in various physiological processes and have consequently become biomarkers for diseases. However, accurate quantification methods have only been established for major compounds, such as amino acids and a limited number of target metabolites. We previously reported a highly sensitive high-throughput method for the simultaneous quantification of amines using 3-aminopyridyl-N-succinimidyl carbamate as a derivatization reagent combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Herein, we report the successful development of a practical and accurate LC-MS/MS method to analyze low concentrations of 40 physiological amines in 19 min. Thirty-five of these amines showed good linearity, limits of quantification, accuracy, precision, and recovery characteristics in plasma, with scheduled selected reaction monitoring acquisitions. Plasma samples from 10 healthy volunteers were evaluated using our newly developed method. The results revealed that 27 amines were detected in one of the samples, and that 24 of these compounds could be quantified. Notably, this new method successfully quantified metabolites with high accuracy across three orders of magnitude, with lowest and highest averaged concentrations of 31.7 nM (for spermine) and 18.3 µM (for α-aminobutyric acid), respectively.