PharmaCenter Bonn & Pharmaceutical Institute, Department of Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, 53121 Bonn, Germany.
Kekulé Institute for Organic Chemistry and Biochemistry, University of Bonn, 53121 Bonn, Germany.
Molecules. 2023 Jun 21;28(13):4887. doi: 10.3390/molecules28134887.
The metalloporphyrin heme acts as the oxygen-complexing prosthetic group of hemoglobin in blood. Heme has been noted to survive for many millions of years in fossils. Here, we investigate its stability and degradation under various conditions expected to occur during fossilization. Oxidative, reductive, aerobic, and anaerobic conditions were studied at neutral and alkaline pH values. Elevated temperatures were applied to accelerate degradation. High-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) identified four main degradation products. The vinyl residues are oxidized to formyl and further to carboxylate groups. In the presence of air or HO, cleavage of the tetrapyrrole ring occurs, and hematinic acid is formed. The highest stability of heme was observed under anaerobic reductive conditions (half-life 9.5 days), while the lowest stability was found in the presence of HO (half-life 1 min). We confirmed that the iron cation plays a crucial role in degradation, since protoporphyrin IX, lacking iron, remained significantly more stable. Under anaerobic, reductive conditions, the above-mentioned degradation products were not observed, suggesting a different degradation pathway. To our knowledge, this is the first molecular taphonomy study on heme, which will be useful for understanding its fate during fossilization.
金属卟啉血红素作为血液中血红蛋白的氧络合辅基。已经注意到，在化石中，血红素可以存活数百万年。在这里，我们研究了在化石形成过程中可能遇到的各种条件下它的稳定性和降解。在中性和碱性 pH 值下研究了氧化、还原、需氧和厌氧条件。升高温度以加速降解。高效液相色谱-串联质谱 (HPLC-MS/MS) 鉴定出四种主要的降解产物。乙烯基残基被氧化形成甲酰基，进一步形成羧基。在空气或 HO 的存在下，四吡咯环发生断裂，形成血红素酸。在厌氧还原条件下，血红素的稳定性最高（半衰期 9.5 天），而在 HO 存在下，稳定性最低（半衰期 1 分钟）。我们证实铁阳离子在降解中起着至关重要的作用，因为缺乏铁的原卟啉 IX 仍然明显更稳定。在厌氧还原条件下，未观察到上述降解产物，这表明存在不同的降解途径。据我们所知，这是血红素的第一个分子埋藏学研究，这将有助于理解其在化石形成过程中的命运。
