Mohanty Ipsita, Moore Samuel G, Biggs Jason S, Freeman Christopher J, Gaul David A, Garg Neha, Agarwal Vinayak
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
University of Guam Marine Laboratory, UOG Station, Mangilao, Guam 96923, United States.
ACS Omega. 2021 Nov 25;6(48):33200-33205. doi: 10.1021/acsomega.1c05685. eCollection 2021 Dec 7.
Together with arginine, the nonproteinogenic amino acid homoarginine is a substrate for the production of vasodilator nitric oxide in the human body. In marine sponges, homoarginine has been postulated to serve as a precursor for the biosynthesis of pyrrole-imidazole alkaloid and bromotyrosine alkaloid classes of natural products. The absolute abundance of homoarginine, its abundance relative to arginine, and its stereochemical assignment in marine sponges are not known. Here, using stable isotope dilution mass spectrometry, we quantify the absolute abundances of homoarginine and arginine in marine sponges. We find that the abundance of homoarginine is highly variable and can far exceed the concentration of arginine, even in sponges where incorporation of homoarginine in natural products cannot be rationalized. The [homoarginine]/[arginine] ratio in marine sponges is greater than that in human analytes. By derivatization of sponge extracts with Marfey's reagent and comparison with authentic standards, we determine the l-isomer of homoarginine to be exclusively present in sponges. Our results shed light on the presence of the high abundance of homoarginine in marine sponge metabolomes and provide the foundation to investigate the biosynthetic routes and physiological roles of this nonproteinogenic amino acid in sponge physiology.
同型精氨酸与精氨酸一起，是人体内产生血管舒张剂一氧化氮的底物。在海洋海绵中，同型精氨酸被推测为吡咯 - 咪唑生物碱和溴酪氨酸生物碱类天然产物生物合成的前体。海洋海绵中同型精氨酸的绝对丰度、其相对于精氨酸的丰度以及其立体化学构型尚不清楚。在此，我们使用稳定同位素稀释质谱法对海洋海绵中同型精氨酸和精氨酸的绝对丰度进行了定量。我们发现，即使在无法合理解释同型精氨酸掺入天然产物的海绵中，同型精氨酸的丰度也高度可变，且可能远远超过精氨酸的浓度。海洋海绵中的[同型精氨酸]/[精氨酸]比值高于人体分析物中的该比值。通过用马尔费试剂对海绵提取物进行衍生化并与标准品进行比较，我们确定同型精氨酸的L - 异构体仅存在于海绵中。我们的结果揭示了海洋海绵代谢组中高丰度同型精氨酸的存在，并为研究这种非蛋白质氨基酸在海绵生理学中的生物合成途径和生理作用奠定了基础。
