Kumamolisin-As (previously called ScpA) is the first known example of a collagenase from the sedolisin family (MEROPS S53). This enzyme is active at low pH and in elevated temperatures. In this study that used x-ray crystallographic and biochemical methods, we investigated the structural basis of the preference of this enzyme for collagen and the importance of a glutamate residue in the unique catalytic triad (Ser 278 -Glu 78 -Asp 82 ) for enzymatic activity. Crystal structures of the uninhibited enzyme and its complex with a covalently bound inhibitor, N-acetyl-isoleucyl-prolyl-phenylalaninal, showed the occurrence of a narrow S2 pocket and a groove that encompasses the active site and is rich in negative charges. Limited endoproteolysis studies of bovine type-I collagen as well as kinetic studies using peptide libraries randomized at P1 and P1, showed very strong preference for arginine at the P1 position, which correlated very well with the presence of a negatively charged residue in the S1 pocket of the enzyme. All of these features, together with those predicted through comparisons with fiddler crab collagenase, a serine peptidase, rationalize the enzyme's preference for collagen. A comparison of the Arrhenius plots of the activities of kumamolisin-As with either collagen or peptides as substrates suggests that collagen should be relaxed before proteolysis can occur. The E78H mutant, in which the catalytic triad was engineered to resemble that of subtilisin, showed only 0.01% activity of the wild-type enzyme, and its structure revealed that Ser 278 , His 78 , and Asp 82 do not interact with each other; thus, the canonical catalytic triad is disrupted.A novel peptidase, initially named ScpA (1) and now called kumamolisin-As (2), was recently identified by us in the culture filtrate of a thermoacidophilic soil bacterium Alicyclobacillus sendaiensis strain NTAP-1 (1). Specificity analyses using macromolecular substrates including globular and other fibrillar proteins showed that kumamolisin-As is highly specific for collagen (3, 4) and thus could be considered as a collagenase, although with some unusual properties. Most noticeably, this enzyme exhibits the maximum activity at acidic pH ϳ4.0. This is in striking contrast to all known collagenases, which are either zinc-dependent metallopeptidases (5) or chymotrypsinlike serine proteinases (6, 7), with an optimum pH for activity at neutral to alkaline regions.A primary structure analysis of this novel "acid collagenase" revealed that it is a member of the sedolisin family, a recently established class of serine peptidases with a unique catalytic triad, Ser-Glu-Asp, in place of the Ser-His-Asp triad of classical serine peptidases (2, 4). Moreover, the enzyme was found to be very similar in its primary structure to kumamolisin, a well characterized member of the family (8 -10), exhibiting 92.7% identity with its mature form. This high level of identity led to the change of the name from the initially used ScpA (1) to kumamolisin-As (2). Kumamolisin-As was the fir...

Enzymatic degradation of collagen produces peptides, the collagen peptides, which show a variety of bioactivities of industrial interest. Alicyclobacillus sendaiensis strain NTAP-1, a slightly thermophilic, acidophilic bacterium, extracellularly produces a novel thermostable collagenolytic activity, which exhibits its optimum at the acidic region (pH 3.9) and is potentially applicable to the efficient production of such peptides. Here, we describe the purification to homogeneity, characterization, gene cloning, and heterologous expression of this enzyme, which we call ScpA. Purified ScpA is a monomeric, pepstatin-insensitive carboxyl proteinase with a molecular mass of 37 kDa which exhibited the highest reactivity toward collagen (type I, from a bovine Achilles tendon) among the macromolecular substrates examined. On the basis of the sequences of the peptides obtained by digestion of collagen with ScpA, the following synthetic peptides were designed as substrates for ScpA and kinetically analyzed: Phe-Gly-Pro-Ala*Gly-Pro-Ile-Gly (k cat , 5.41 s ؊1 ; K m , 32 M) and Met-Gly-ProArg*Gly-Phe-Pro-Gly-Ser (k cat , 351 s ؊1 ; K m , 214 M), where the asterisks denote the scissile bonds. The cloned scpA gene encoded a protein of 553 amino acids with a calculated molecular mass of 57,167 Da. Heterologous expression of the scpA gene in the Escherichia coli cells yielded a mature 37-kDa species after a two-step proteolytic cleavage of the precursor protein. Sequencing of the scpA gene revealed that ScpA was a collagenolytic member of the serine-carboxyl proteinase family (the S53 family according to the MEROPS database), which is a recently identified proteinase family on the basis of crystallography results. Unexpectedly, ScpA was highly similar to a member of this family, kumamolysin, whose specificity toward macromolecular substrates has not been defined.Collagen is an insoluble structural protein that accounts for approximately 30% of the total weight of animal proteins and is produced in large quantities as a by-product in livestock industries. It has recently been shown that the enzymatic degradation of collagen as well as that of gelatin, a denatured form of collagen, allows efficient utilization of these structural proteins. This degradation produces peptides, the collagen peptides, which have been shown to have several biological activities of industrial and medical interest (27), leading to the establishment of a wide variety of applications, e.g., an immunotherapeutic agent (7, 9), a moisturizer for cosmetics, a preservative (2), and seasoning and dietary materials (4).Generally, the enzymatic degradation of collagen is not affected by ordinary digestive proteinases but requires the collagen-specific, Zn 2ϩ -dependent metalloproteinases (collagenases). Although microbial collagenases have been found in a wide variety of mesophilic bacterial strains (3), the industrialscale application of known bacterial collagenases for collagen peptide production has been hampered because of their insufficient stability. In 2000...

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Copepods are the dominant taxa in zooplankton communities of the ocean worldwide. Although bioluminescence of certain copepods has been known for more than a 100 years, there is very limited information about the structure and evolutionary history of copepod luciferase genes. Here, we report the cDNA sequences of 11 copepod luciferases isolated from the superfamily Augaptiloidea in the order Calanoida. Highly conserved amino acid residues in two similar repeat sequences were confirmed by the multiple alignment of all known copepod luciferases. Copepod luciferases were classified into two groups of Metridinidae and Heterorhabdidae/Lucicutiidae families based on phylogenetic analyses, with confirmation of the interrelationships within the Calanoida using 18S ribosomal DNA sequences. The large diversity in the specific activity of planktonic homogenates and copepod luciferases that we were able to express in mammalian cultured cells illustrates the importance of bioluminescence as a protective function against predators. We also discuss the relationship between the evolution of copepod bioluminescence and the aspects of their ecological characteristics, such as swimming activity and vertical habitat.

Abstract. NIP-142 is a novel benzopyran compound that was shown to prolong the atrial effective refractory period and terminate experimental atrial fibrillation in the dog. In the present study, we examined the effects of NIP-142 on isolated guinea pig myocardium and on the Gprotein-coupled inwardly rectifying potassium channel current (acetylcholine-activated potassium current; I KACh ) expressed in Xenopus oocytes. NIP-142 (10 and 100 µM) concentration-dependently prolonged the refractory period and action potential duration in the atrium but not in the ventricle. E-4031 and 4-aminopyridine prolonged action potential duration in both left atrium and right ventricle. Prolongation by NIP-142 of the atrial action potential duration was observed at stimulation frequencies between 0.5 and 5 Hz. In contrast, the prolongation by E-4031 was not observed at higher frequencies. Tertiapin, a blocker of I KACh , prolonged action potential duration in the atrium but not in the ventricle. NIP-142 completely reversed the carbachol-induced shortening of atrial action potential duration. NIP-142 (1 to 100 µM), as well as tertiapin (0.1 to 100 nM), concentration-dependently blocked I KACh expressed in Xenopus oocytes; the blockade by NIP-142 was not affected by membrane voltage. In conclusion, NIP-142 was shown to prolong atrial refractory period and action potential duration through blockade of I KACh which may possiblly explain its previously described antiarrhythic activity. NIP-142 has pharmacological properties that are different from classical class III antiarrhythmic agents such as atria specificity and lack of reverse frequency dependence, and thus appears promising for the treatment of supraventricular arrhythmia.