Antioxidative Potency of Dolphin Serum Albumin Is Stronger Than That of Human Serum Albumin Irrespective of Substitution of 34Cysteine With Serine.

Miwa Suzuki,Makoto Anraku,Tomoko Endoh,Takushi Kishida,Keiichi Ueda,Wataru Hakamata

doi:10.3389/fphys.2020.598451

Abstract

Serum albumin (SA), the most abundant protein in circulation, functions as a carrier protein, osmoregulator, and antioxidant. Generally, SA exerts its antioxidative effects by scavenging reactive oxygen species. Because marine mammals are superior divers, they are intermittently exposed to oxidative stress induced by rapid reperfusion of oxygen to ischemic tissues after the dive. Although several antioxidants in marine mammals have been described, SA activity remains largely uncharacterized. In this study, we investigated the antioxidative activity of SA in marine mammals by comparing features of the primary and steric structures, biochemical properties, and antioxidative activities of common bottlenose dolphin SA (DSA) and human SA (HSA). Our results revealed that DSA lacked free cysteine at position 34 that is important for the antioxidative activity of HSA; however, the antioxidative capacity and thiol activity of DSA were stronger than those of HSA. Circular dichroism spectra showed different patterns in DSA and HSA. Ultraviolet fluorescence intensities of DSA were higher than those of HSA, suggesting lower surface hydrophobicity of DSA. Additionally, DSA showed higher excess heat capacity than HSA. We then compared a homology model of DSA with a 3D model of HSA. Our results indicate that DSA was more unstable than HSA at least in the body-temperature range, probably due to the mode of molecules involved in the disulfide bonds and/or the lower surface hydrophobicity, and it may be related to the equivalent or stronger antioxidant potency of DSA. These data show that DSA is an effective antioxidant in the circulation of the dolphin.

Highlights

Marine mammals habitually dive to feed, avoid predators, and rest (Thompson et al, 1991; Boyd, 1997; Heithaus and Frid, 2003; Sparling et al, 2007)
The comparison revealed that 34Cys of serum albumin (SA), which is a critically important residue for the antioxidative activity of human SA (HSA), was replaced with Ser in most the sequenced cetacean species with the exception of Yangtze River dolphin (Table 1)
Spectral data collected in the range of 200–250 nm (Figure 1A) demonstrated that dolphin SA (DSA) showed a different pattern from that of HSA, with increased average residue ellipticity

Summary

Introduction

Marine mammals habitually dive to feed, avoid predators, and rest (Thompson et al, 1991; Boyd, 1997; Heithaus and Frid, 2003; Sparling et al, 2007). During diving, they undergo cardiovascular adjustments for oxygen consumption. Restriction of blood flow leads to ischemia of peripheral tissues, while reperfusion with tachycardia after diving induces production of reactive oxygen species (ROS) in these tissues (VázquezMedina et al, 2007; Zenteno-Savin et al, 2012; Chouchani et al, 2014) Generally, antioxidants counteract oxidative stress (Pisoschi and Pop, 2015). More than 50% of the total antioxidative activity of plasma is due to SA (Roche et al, 2008; Taverna et al, 2013)

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Results

Conclusion