Abiotic transformation of labile protein to refractory protein in sea water

• Published in: Marine chemistry 1994, Vol.45 (3), p.187-196
• Main Authors: Keil, Richard G, Kirchman, David L
• Format: Article
• Language: English
• Subjects: Analytical biochemistry: general aspects, technics, instrumentation; Analytical, structural and metabolic biochemistry; Animal, plant and microbial ecology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; General aspects; Marine; Microbial ecology
• ISSN: 0304-4203; 1872-7581
• DOI: 10.1016/0304-4203(94)90002-7

In order to determine if organic matter dissolved in sea water may undergo abiotic alterations that make it resistant to microbial degradation, the protein ribulose 1,5-bisphosphate carboxylase (RuBPcase) was abiotically aged in sterile sea water and then exposed to natural bacterial assemblages. Rates of protein assimilation decreased when protein was aged as little as 6 h; protein aged for 40 days was degraded 4-fold more slowly than non-aged protein. Abiotic modification rates, calculated from decreases in degradation rate with increasing aging time, were highest during the initial day of aging (0.8–4.8 d −1) and then decreased to 0.03 d −1. No aging effect was observed in organic-free sea water, indicating that organic-organic interactions produced the refractory protein. Amino acids from the protein were fully recovered after acid hydrolysis, indicating that the decreased lability was not caused by acid-stable molecular changes to the protein. Abiotic complexation of labile organic compounds with existing DOM may be a critical first step in the formation of refractory organic materials.