Relationships of Matrix Metalloproteinase 1 and a Tissue Inhibitor of Metalloproteinase to Collagen Metabolism in Haliotis discus hannai.

In response to physical, chemical, and/or biological stimuli, considerable tissue self-degradation occurs in abalone, causing severe post-harvest quality loss. During this process, the extracellular matrix (ECM) is greatly degraded by endogenous proteases. The main component of the ECM is collagen, primarily type I collagen. Although the activity of matrix metalloproteinases (MMPs), which can specifically degrade collagen, is precisely regulated by tissue inhibitors of MPs (TIMPs), indicating that MMPs and TIMPs play crucial roles in the regulation of tissue self-degradation, few studies have reported the interaction between MMPs and TIMPs. In this study, we reveal collagenases to participate in postmortem tissue self-degradation of Haliotis discus hannai by degrading type I collagen. The recombinant MMP-1 catalytic domain (rMMP1c) of abalone with high purity and enzyme activity is expressed using a prokaryotic expression system. The optimum temperature and pH for rMMP1c are 37 °C and 7.0, respectively. The thermal denaturation temperature of rMMP1c is 67.0 ± 0.9 °C. Ethylenediamine tetraacetic acid (EDTA) and 1,10-phenanthroline can completely inhibit rMMP1c activity, while Ba2+, Ca2+, and Mg2+ can significantly elevate it. TIMP is also expressed using HEK 293F cells. Recombinant TIMP (rTIMP) shows good inhibitory activity toward rMMP1c. Inhibition kinetics analyses reveal rTIMP to be a competitive inhibitor of rMMP1c. Biolayer interferometry reveals that rTIMP can effectively bind with rMMP1c, with an equilibrium dissociation constant value of 263 nM. rMMP1c effectively degrades type I collagen γ-ß-α chains in turn, and rTIMP can significantly inhibit rMMP1c degradation activity. These results provide a theoretical basis for the study of MMP and TIMP interaction and elucidate the possible mechanism for abalone tissue self-degradation.

Suppressive Interaction Approach for Masking Stale Note of Instant Ripened Pu-Erh Tea Products.

The unpleasant stale note is a negative factor hindering the consumption of instant ripened Pu-erh tea products. This study focused on investigating volatile chemicals in instant ripened Pu-erh tea that could mask the stale note via sensory evaluation, gas chromatography-mass spectrometry (GC-MS), and gas chromatography-olfactometry (GC-O) analyses. GC-MS and GC-O analyses showed that linalool, linalool oxides, trans-ß-ionone, benzeneacetaldehyde, and methoxybenzenes were the major aroma contributors to the simultaneous distillation and extraction (SDE) extract of instant ripened Pu-erh tea. Sensory evaluation showed that the SDE extract had a strong stale note, which was due to methoxybenzenes. By investigating suppressive interaction among flavour components, the stale note from methoxybenzenes was shown to have reciprocal masking interactions with sweet, floral, and green notes. Moreover, the validation experiment showed that the addition of 40 µg/mL of trans-ß-ionone in the instant ripened Pu-erh tea completely masked the stale note and improved the overall aromatic acceptance. These results elucidate the volatile chemicals that could mask the stale note of instant ripened Pu-erh tea products, which might help to develop high quality products made from instant ripened Pu-erh tea.

Preparation, characterisation and use for antioxidant oligosaccharides of a cellulase from abalone (Haliotis discus hannai) viscera.

BACKGROUND: In China, abalone (Haliotis discus hannai) production is growing annually. During industrial processing, the viscera, which are abundant of cellulase, are usually discarded or processed into low-value feedstuff. Thus, it is of interest to obtain cellulase from abalone viscera and investigate its application for preparation of functional oligosaccharides. RESULTS: A cellulase was purified from the hepatopancreas of abalone by ammonium sulfate precipitation and two-steps column chromatography. The molecular weight of the cellulase was 45 kDa on SDS-PAGE. Peptide mass fingerprinting analysis yielded 103 amino acid residues, which were identical to cellulases from other species of abalone. Substrate specificity analysis indicated that the cellulase is an endo-1,4-ß-glucanase. Hydrolysis of seaweed Porphyra haitanensis polysaccharides by the enzyme produced oligosaccharides with degree of polymerisation of two to four, whose monosaccharide composition was 58% galactose, 4% glucose and 38% xylose. The oligosaccharides revealed 2,2'-diphenyl-1-picrylhydrazyl free radical as well as hydrogen peroxide scavenging activity. CONCLUSION: It is feasible and meaningful to utilise cellulase from the viscera of abalone for preparation of functional oligosaccharides. © 2015 Society of Chemical Industry.