Food Biochemistry and Food Processing (2 edition)

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270 Part 2: Biotechnology and Enzymology

Table 14.3.Muscle Proteases from Marine Animals

Major Group Family Enzyme Purified Organism Reference

Lysosomal cathepsin Cysteine Cathepsin A Carp Toyohara et al. (1982)

Milkfish Jiang et al. (1990)

Atlantic cod McLay (1980)

Cathepsin B Carp Makinodan and Ikeda (1971)

Grey mullet Bonete et al. (1984)

Tilapia Sherekar et al. (1988)

Mackerel Aoki et al. (2002)

Cathepsin C Atlantic squid Hameed and Haard (1985)

Pacific whiting Erickson et al. (1983)

Cathepsin L Chum salmon Yamashita and Konagaya (1990)

Spotted mackerel Lee et al. (1993)

Anchovy Heu et al. (1997)

Pacific whiting Visessanguan et al. (2001)

Aspartic Cathepsin D True sardine Klomklao et al. (2008)

Herring Nielsen and Nielsen (2001)

Alkaline proteases Serine Trypsin-like Atlantic menhaden Choi et al. (1999)

Bigeye snapper Benjakul et al. (2003a)

Neutral proteases Cysteine Calpains Tilapia Wang et al. (1993)

Octopus Hatzizisis et al. (1996)

Sea bass Ladrat et al. (2000)

Rainbow trout Saito et al. (2007)

Metalloprotease Neutral metalloprotease Crucian carp Kinoshita et al. (1990)

Two cathepsin A-like proteases (15.6 kDa and 35.6 kDa) have

been purified from milkfish muscle and had optimal activity

with carbobenzoyl-l-Gly-l-Phe at pH 7.0 (Jiang et al. 1990).

Cathepsin A, partially purified from Atlantic cod muscle, hy-

drolyzed carbobenzoyl-α-Glutamyl-l-Tyr with an optimum of

pH 5.0 (McLay 1980). Cathepsin A-like activity has also been

detected in muscle of tilapia, Bombay duck, pomfret, and shrimp

by Sherekar et al. (1988) but was not detected in cod muscle

(Shahidi and Kamil 2001).

Cathepsin B (EC 3.4.22.1) is the best known and most thor-

oughly investigated lysosomal thiol protease. It is now recog-

nized that at least two enzymes have this activity including

cathepsin B (B 1 )andB 2. Cathepsin B 1 is a thiol endopepti-

dase, having a MW of 24–28 kDa with a pH of 5.0–5.2, and

maximal activity at pH 6.0. In contrast, cathepsin B 2 is an ex-

opeptidase also called carboxypeptidase B, with a MW ranging

between 47 kDa and 52 kDa (Kang and Lanier 2000). Cathep-

sin B 3 , now called cathepsin H, is a 25-kDa glycoprotein that is

very heat stable. Cathepsin B purified from carp (Makinodan and

Ikeda 1971), grey mullet (Bonete et al. 1984), tilapia (Sherekar

et al. 1988), and mackerel (Aoki et al. 2002) had the MWs of

23–29 kDa and optimal pH range of 5.5–6.0. Aoki et al. (2002)

reported that cathepsin B purified from the white muscle of com-

mon mackerel had a MW of 23 kDa. The optimal pH for activity

was 5.5.

Cathepsin C (EC 3.4.4.9), an exopeptidase, is also called

dipeptidyl transferase and dipeptidyl-aminopeptidase. It was

first recognized as an enzyme that deaminates Gly-Phe-NH 2.

It is unlikely to act on intact proteins directly, but rather has

the highest specific activity among all the lysosomal peptidase,

suggesting that it further digests the resulting peptide fragments

by cathepsin D. It is an oligomeric thiol protease with a MW

of 200 kDa requiring Cl−ions for activity (Ashie and Simp-

son 1997). The enzyme is optimally active within a pH range

of 5–6 (Ashie and Simpson 1997). Hameed and Haard (1985)

reported that cathepsin C extracted from Atlantic squid muscle

had MW of 25 kDa and was Cl−and sulfhydryl dependent, being

inhibited by sulfhydryl enzyme inhibitors, such as iodoacetate,

PCMB, and HgCl 2. For cathepsin C from sarcoplasmic fluid of

Pacific whiting, it showed the maximal activity at pH 7.0, which

was greater than the maximal activity obtained at pH 6.0 in cod

(Erickson et al. 1983).

Cathepsin D (EC 3.4.4.23) is a major lysosomal aspartic pro-

tease, which is involved in the cellular degradation of proteins

(Nielsen and Neilsen 2001). Cathepsin D is a 42–60 kDa en-

dopeptidase that is active within a pH range of 3–5. It exists in

several isomeric forms with pH ranging between 5.7 and 6.8,

and exhibits a broad range of activity on muscle tissue between

pH 3.0 and 6.0 (Ashie and Simpson 1997). The enzyme prefer-

entially cleaves peptide bonds between hydrophobic amino acid

residues (Ashie and Simpson 1997). Cathepsin D is strongly in-

hibited by pepstatin A, a specific inhibitor of carboxyl proteases,

whereas thiol protease inhibitors have negligible effects on en-

zyme activity (Bonete et al. 1984). Cathepsin D was purified

from herring muscle. The purified enzyme is a monomer with a

MW of 38–39 kDa. It is inhibited by pepstatin and has an optimal

activity at pH 2.5 when hemoglobin is used as the substrate. The

isoelectric point is 6.8 (Nielsen and Nielsen 2001). Klomklao