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The 66 K-da Protein Identified as a Light Meromyosin Is Involved in the Setting of Surimi

A.K.M. Nowsad Alam
Department of Fisheries Technology, Bangladesh Agricultural University Mymensingh 2202, Bangladesh

E. Niwa Faculty of Bioresources
Mie University, Kamihama 1515, Tsu, Mie 514, Japan

Abstract/ Executive Summary:

The 66 kilo-Dalton (kDa) protein split off from the crosslinked myosin heavy chain (CMHC) formed due to the setting of Alaska pollack surimi, frozen-storage of Pacific cod flesh, and vinegar-curing of Pacific mackerel mince was identified as a light meromyosin (LMM). Puncture and stress-relaxation tests showed that the actomyosin subunits (AMS) of Alaska pollack surimi, upon setting at 30°C, transformed into gel, although the elasticity of this gel was very low when compared to the gels from surimi or actomyosin (AM). Electrophoretic studies showed that the band due to LMM in the gel from AMS gradually disappeared with the progress of setting but higher molecular weight polymer did not form. The intensity of the bands due to other myosin sub-fragments decreased a little. The findings suggest that at setting temperature, LMM of MHC molecule leads to an unfolding resulting in an intramolecular aggregation through non-covalent interactions, and thus plays a significant role in the crosslinking of MHC.

Keywords: Surimi, Light meromyosin, Non-covalent aggregation

Location: Department of Fisheries Technology, Bangladesh Agricultural University Mymensingh 2202, Bangladesh

Start Date:

End Date:

Program Area: Food Safety and Security

Commodity: Fish farming, Protein

Objectives:

To identify the 66 kDa protein tentatively identified as a light meromyosin (LMM) and to exam the role of this MHC subfragment in the setting of surimi.

Methodology:

SA-grade (Super-A grade) unsalted frozen surimi of Alaska pollack from Golden Alaska Seafoods Inc., Seattle, WA, U.S.A. was used. Pacific cod Gadus macrocephalus and Pacific mackerel Pneumatophorus japonicus were purchased from a retail fish store in Tsu city, Japan. Both trypsin (bovine pancreas) and trypsin inhibitor (soybean) were obtained from Sigma Chem. Co. U.S.A. Extraction of AM Mince of Alaska pollack surimi and dorsal and lateral muscles of Pacific cod were washed three times with 5 volumes of 3.38 mM NaH2P04-15.5 mM Na2HP04 (pH 7.5), followed by centrifugation at 6,000 x g for 10 min. AM was extracted for 3 h with 5 volumes of 0.8 M I.

Source of Information: Bangladesh J. Fish. Res., 1 (1) : 73-82

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The results of the present study apparently differ from that of Chan eta/. (op cit) since LMM was mostly crosslinked within one hour of setting at 30°C. In fact, larger myosin subfragments like HMM and S-1 were mostly cleaved into smaller ones in this study. Therefore, the exact influence of these subfragments can not be understood and explained from these results. Nonetheless, it seems that MHC molecule may lead to an unfolding of the super helix of the tail at setting temperatures, exposing hydrophobic residues to the polar environments, resulting in the intramolecular crosslinking through non-covalent bonds among the subfragment proteins that cleaved from the tail portion of the molecule. This may be further entangled with the intermolecular crosslinking of MHC itself and locked up in CMHC at the top of the SDS-PAGE disc gel which could split off again from CMHC in concentrated urea, as we explained elsewhere (Nowsad eta/. 1993).

Knowledge Management: Journal