Crystals from cocoons of Malacosoma neustria testacea.

The crystalline material covering the cocoon of Malacosoma neustria testacea (Lasiocampidae, Lepidoptera) was analyzed physically and chemically. The mean component was identified as calcium oxalate monohydrate, and the crystals were found to be whewellite in form.

Novel cysteine proteinase inhibitors homologous to the proregions of cysteine proteinases.

Propeptides of papain-like cysteine proteinases such as papain, cathepsins B, L and S are potent inhibitors of their cognate cysteine proteinases with Ki values in the nanomolar range, and they exhibit highest inhibition selectivity for enzymes from which they originate. Recent studies have identified novel inhibitor proteins that are homologous to the proregions of papain-like cysteine proteinases. Mouse activated T-lymphocytes express cytotoxic T-lymphocyte antigen (CTLA-2), which is homologous to the proregion of mouse cathepsin L. CTLA-2 exhibits inhibitory activities to several cysteine proteinases. We have also identified a similar propeptide-like cysteine proteinase inhibitor, Bombyx cysteine proteinase inhibitor (BCPI), in the silkmoth Bombyx mori. BCPI is a slow and tight binding inhibitor of cathepsin L-like cysteine proteinases with Ki values in picomolar range, and the inhibition is highly selective towards these proteinases just like the propeptides. Recent genome analyses have shown the expression of similar propeptide-like proteins in Drosophila and rat, suggesting the presence of a novel class of cysteine proteinase inhibitors in a variety of organisms. Studies of the gene structures and phylogenetic analysis have shown that genes of the propeptide-like cysteine proteinase inhibitors have emerged from ancestor genes of their parental enzymes.

Phosphorylation by Ca2+/calmodulin-dependent protein kinase II and protein kinase C of sepiapterin reductase, the terminal enzyme in the biosynthetic pathway of tetrahydrobiopterin.

Sepiapterin reductase, the terminal enzyme in the biosynthetic pathway of tetrahydrobiopterin, was stoichiometrically phosphorylated by Ca2+/calmodulin-dependent protein kinase II and protein kinase C (Ca2+/phospholipid-dependent protein kinase) in vitro. Maximal incorporation of phosphate into the enzyme subunit by these was 3.05 +/- 0.05 (n = 4) and 0.74 +/- 0.03 (n = 5) 32P mol per mol enzyme subunit, respectively. The enzyme was not phosphorylated by cyclic nucleotide-dependent protein kinase of either the cAMP-dependent or cGMP-dependent type in this study. Dihydropteridine reductase, another enzyme working in direct supply of tetrahydrobiopterin, was also a good substrate for Ca2+/calmodulin-dependent protein kinase II. Phosphorylation of sepiapterin reductase by these protein kinases modified the kinetic properties of the enzyme. It is likely that these multifunctional Ca(2+)-activated protein kinases may play a role in the regulation of the physiological function of the BH4-generating enzymes in vivo, as was previously found in the case of BH4-requiring enzymes.

A novel inhibitor protein for Bombyx cysteine proteinase is homologous to propeptide regions of cysteine proteinases.

A cDNA clone for an inhibitor of Bombyx cysteine proteinase was isolated and sequenced. Active inhibitor proteins were expressed in Escherichia coli using the cDNA. The open reading frame of the cDNA encodes a 105 residues protein with 19 residues of a signal sequence. The inhibitor has amino acid sequences homologous to several cysteine proteinases, but only to their propeptide sequences. The results suggest that some cysteine proteinase proregions may have evolved as autonomous modules and become inhibitor proteins for cysteine proteinases.

Occurrence of thiol proteinases in the eggs of the silkworm, Bombyx mori.

In the crude extract of matured eggs of the silkworm (Bombyx mori), proteolytic activity was detected only in the acidic pH region with maximal activity at pH 3.5, and this activity was maintained throughout the development. No appreciable activity was observed in the neutral to alkaline pH region either in matured eggs or in eggs at early embryonic stages. Two molecular forms of proteinases active at pH 3.5 were obtained from matured eggs, and their molecular weights were estimated to be over 16,000 and about 68,000 respectively. An additional form of 40,000 molecular weight appeared in eggs just before hatching. They were strongly inhibited by thiol proteinase inhibitors, such as p-chloromercuribenzoate (pCMB), p-chloromercuriphenyl sulfonate (pCMPS), and N-[N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucyl]agmatine (E-64), whereas pepstatin, diisopropylphosphorofluoridate, and EDTA were without effect, suggesting that they are thiol enzymes. They hydrolyzed casein, bovine serum albumin, egg albumin, and gamma-globulin. They could not hydrolyze alpha-N-benzoyl-DL-arginine p-nitroanilide, alpha-N-benzoyl-DL-arginine beta-naphthylamide, and several other synthetic substrates. These thiol proteinases are different from animal tissue thiol proteinases hitherto known.

Cysteine proteinase from the eggs of the silkmoth, Bombyx mori: identification of a latent enzyme and characterization of activation and proteolytic processing in vivo and in vitro.

When an acid cysteine proteinase, which had been purified from the eggs of silkmoth, Bombyx mori, was incubated at pH 3.6, enzymatic activity appeared after a few minutes, lag period, indicating that the purified cysteine proteinase was a latent form. SDS-polyacrylamide gel electrophoresis showed that after the incubation the latent form of the enzyme (47 kDa) disappeared and the active (39 kDa) form of the enzyme appeared, suggesting that the latent form was processed to the active form under acidic conditions (pH 3.6). The NH2-terminal 22-residue sequence of the active form was determined. The conversion of the latent form to the active form was completely blocked by E-64, which is a specific inhibitor of cysteine proteinases. The results strongly suggest that the processing might be autocatalytic. The latent form (47 kDa) disappeared in the silkmoth eggs during embryonic development and concomitantly with its disappearance, the 39-kDa form appeared, indicating that in vivo the enzyme is activated in a similar manner to that observed in in vitro experiments.

Molecular cloning and sequencing of cDNA that encodes cysteine proteinase in the eggs of the silkmoth, Bombyx mori.

We have isolated and sequenced a 1,486-base-pair near full-length cDNA coding for Bombyx egg cysteine proteinase. The cDNA encodes 344 amino acid residues containing a typical signal peptide sequence (16 residues), pro-peptide (104 residues), and the sequence for mature enzyme (224 residues). Sequence alignments show that the egg cysteine proteinase is similar to lobster cysteine proteinase (61% identity), barley cysteine proteinase, Aleurain (52%), rice cysteine proteinase, Oryzain (54%), and rat cathepsin L (59%). The amino-terminal sequencing of the egg cysteine proteinase indicates that the enzyme purified as an inactive form from eggs is a pro-enzyme. Pro-egg cysteine proteinase was detected in other silkmoth tissues such as ovary, fat body, hemocyte, and hemolymph by immunoblotting.

Bombyx cysteine proteinase inhibitor (BCPI) homologous to propeptide regions of cysteine proteinases is a strong, selective inhibitor of cathepsin L-like cysteine proteinases.

Bombyx cysteine proteinase inhibitor (BCPI) is a novel cysteine proteinase inhibitor. The protein sequence is homologous to the proregions of certain cysteine proteinases. Here we report the mechanism of its inhibition of several cysteine proteinases. BCPI strongly inhibited Bombyx cysteine proteinase (BCP) activity with a K(i) = 5.9 pM, and human cathepsin L with a K(i) = 36 pM. The inhibition obeyed slow-binding kinetics. The inhibition of cathepsin H was much weaker (K(i) = 82 nM), while inhibition of papain (K(i) > 1 microM) and cathepsin B (K(i) > 4 microM) was negligible. Following incubation with BCP, BCPI was first truncated at the C-terminal end, and then gradually degraded over time. The truncation mainly involved two C-terminal amino acid residues. Recombinant BCPI lacking the two C-terminal amino acid residues still retained substantial inhibitory activity. Our results indicate that BCPI is a stable and highly selective inhibitor of cathepsin L-like cysteine proteinases.

In vivo activation of pro-form Bombyx cysteine protease (BCP) in silkmoth eggs: localization of yolk proteins and BCP, and acidification of yolk granules.

The present study was designed to investigate the process of acidification of yolk granules during embryogenesis. In oocytes of mature Bombyx mori silkmoth, yolk proteins and a cysteine protease (pro-form BCP) were found in yolk granules. BCP was localized in small sized yolk granules (SYG, 3-6 microm in diameter) and yolk proteins in large sized granules (LYG, 6-11 microm in diameter), which might result in a spatial separation of protease and its substrates to avoid unnecessary hydrolysis. The granules were isolated on Percoll density gradient centrifugation. Although separation of LYG and SYG was incomplete, the granules sedimented in different fractions when using unfertilized egg extract, in which LYG was recovered from heavier fractions and BCP from lighter fractions. Acid phosphatase, as well as other lysosomal marker enzymes tested, was recovered from LYG-containing fractions. When extracts were prepared from developing eggs (day 3), some BCP-containing granules co-sedimented with LYG. The inactive pro-form BCP was activated in vivo, in parallel with yolk protein degradation, and as demonstrated previously in vitro under acidic conditions (). These results suggest that acidification occurs in yolk granules during embryogenesis. This was also confirmed using acridine orange fluorescent dye. In early development, most yolk granules were neutral, but became acidic during embryonic development. SYG were progressively recovered in heavier density fractions, displaying acidic interior. In this fraction, BCP-containing granules seem to be associated with larger granules (6-11 microm in size). In addition, SYG (BCP containing granules) were likely to be acidified earlier than LYG. Our results suggest that acidification initiates yolk degradation through activation of pro-form BCP.

The cDNA sequence encoding bovine SP-22, a new defence system against reactive oxygen species in mitochondria.

We have isolated cDNA clones coding SP-22, an antioxidant protein in mitochondria, from a bovine adrenal medulla cDNA library constructed with (lambda)gt11. The largest clone contained the entire coding sequence for mature SP-22. Since the isolated cDNA clones lacked 5'- and 3'-ends, we determined the sequences of both ends by the "Rapid Amplification of cDNA Ends (RACE)" tecnique. The deduced amino acid sequence of the mature protein region was the same as that determined by protein sequencing. Since SP-22 had a mitochondrial targetting signal, its mitochondrial localization was confirmed.

Trehalases from the male accessory glands of the American Cockroach: developmental changes and the hormonal regulation of the enzymes.

Two types of trehalases, designated CM-I and CM-II, were detected in the male accessory gland of the American cockroach and they could be separated by CM-cellulose chromatography (S. Y. Takahashi, S. Higashi, S. Minoshima, M. Ogiso, and K. Hanaoka, 1980, Int. J. Invert. Reprod. 2, 373-381). Trehalase activity in the gland showed a rapid increase after adult emergence. The relative activities of the two enzymes were followed separately during adult development. The appearance of CM-II preceded that of CM-I during adult development. Allatectomy and decapitation of newly molted adults resulted in inhibition of the increase of enzyme activity, and in the allatectomized cockroach, CM-II, which is the major enzyme activity in the gland, was missing. Implantation of the corpora allata as well as application of JH-III and the JH analogs isopropyl-11-methoxy-3,7,11-trimethyl-2,4,-dodecadienoate (ZR-515) and 6,7-epoxy-1-(p-ethylphenoxy)-3,7-dimethyl-2-octene (R-20458) into the decapitated animals restored the enzyme activities. The data suggested that trehalase in the male accessory gland was under the control of the corpora allata. The regulation of trehalase activity in the male accessory gland was discussed with respect to its function.

Purification and characterization of a cysteine proteinase from silkworm eggs.

Eggs of the silkworm, Bombyx mori, contain a high level of a proteinase which is most active in acidic pH region. The proteinase was purified from an extract of eggs by a six-step procedure which included conventional chromatographic fractionations. The molecular mass of the proteinase was estimated to be 350 kDa by gel filtration and 47 kDa by electrophoresis on sodium dodecyl sulfate/polyacrylamide gels, suggesting an octameric structure. The amino acid composition was found to resemble that of mammalian lysosomal cysteine proteinases, in particular cathepsin L. The NH2-terminal 10-residue sequence is Val-Gln-Phe-Phe-Asp-Leu-Val-Lys-Glu-Glu-. The enzyme appears to be a member of the class of cysteine proteinases since it was strongly inhibited by sulfhydryl-reactive compounds and N-[N-(1,3-trans-carboxyoxiran-2-carbonyl)-L-leucyl]-agmatine (E-64). The enzyme hydrolyzed various protein substrates, such as hemoglobin, vitellogenin, vitellin, and lipophorin, with maximal activity around pH 3-3.5. The specificity of the cleavage sites in the oxidized B chain of insulin was rather well defined and there was high affinity for hydrophobic residues at the P2 and P3 positions. The cysteine proteinase is thought to be involved in protein degradation during embryonic development of silkworm eggs.

Intracellular transduction mechanisms for the slow synaptic events.

Electrical activities of the postganglionic neurons in the superior cervical ganglia of rabbits are modulated in various ways following activation of the subtypes of muscarinic acetylcholine receptors. (i) M1 receptors mediate a slow depolarization consisting of at least three types of ionic conductance changes, and one of these is possibly mediated by cyclic GMP. (ii) M2 receptors mediate a slow hyperpolarization that seems to be generated by inositol triphosphate derived from phosphatidylinositol breakdown. (iii) M2 receptors also cause, through an activation of C kinase, a suppression of Ca entry during action potentials that results in a characteristic change in the action potentials and thereby modulates excitability of superior cervical ganglion neurons. Each subtype of muscarinic receptors thus regulates different pathways of intracellular transduction and modulates the electrical signaling of sympathetic neurons.

Cyclic GMP-dependent protein kinase and phosphorylation of the endogenous substrate proteins in the rabbit superior cervical ganglion.

When the homogenate of rabbit superior cervical ganglia (SCG) was incubated in the presence of [gamma-32P]ATP and Mg2+, two specific proteins were strongly labeled. Their apparent molecular weights were 90,000 and 54,000, respectively. The phosphorylation of the latter was significantly stimulated by 10-50 nM cyclic GMP but to a lesser extent by cyclic AMP, whereas that of the former was not stimulated significantly by either of the cyclic nucleotides. The purified protein kinase inhibitor from rabbit skeletal muscle did not inhibit the phosphorylation. These results indicated that the observed phosphorylation of 54K protein was dependent on cyclic GMP but not on cyclic AMP. When intact SCG was incubated in the presence of 32Pi, phosphorylation of 90K protein was stimulated by cyclic GMP, dibutyryl cyclic GMP, and 8-bromo-cyclic GMP (10 microM), whereas phosphorylation of 54K protein was not significantly stimulated by any of these substances. The present demonstration of endogenous cyclic GMP-dependent protein kinase activity and its endogenous substrate proteins raises a possibility that the physiological actions of cyclic GMP in SCG are mediated by the phosphorylation of these proteins.

Autolytic activation mechanism of Bombyx acid cysteine protease (BCP).

Acid cysteine proteinase in the eggs of the silkmoth, Bombyx mori, exists as an inactive proenzyme. This 47-kDa pro-BCP1 zymogen molecule can be processed in vitro into an enzymatically active 39-kDa BCP molecule. In this current study, the maximum rate of processing in vitro was achieved at approximately pH 4.0, at a temperature of 37 degrees C under reducing conditions. The rate of conversion was not affected by increasing concentrations of pro-BCP. We prepared immobilized BCP bound to AH-Sepharose and examined the activation. Immobilized pro-BCP was autolysed, although the rate of processing was slow, indicating that the reaction might be an intramolecular one. Kinetic experiments suggest that the mechanism is likely to involve a stepwise reaction, in which pro-BCP is converted to an active enzyme through intermediate forms releasing small peptides stepwise. The results suggest that autocatalytic cleavage (intramolecular) is a major processing step in the early stage of pro-BCP activation.

Purification and characterization of Bombyx cysteine proteinase specific inhibitors from the hemolymph of Bombyx mori.

Protein inhibitors capable of inhibiting BCP (Bombyx cysteine proteinase) were found in the larval-pupal hemolymph of Bombyx mori. Two forms of the inhibitors, named BCPI (BCP inhibitor) alpha and BCPI beta, were purified from the pupal hemolymph by heat treatment and column chromatographies on CM-cellulose, Toyopearl HW-50, Phenyl-Sepharose, and Mono Q. Purified BCPI beta gave a single protein band with a molecular mass of 10,500 daltons on SDS-PAGE. BCPI alpha is mostly composed of the same molecular mass protein as BCPI beta. Both forms were inhibitory towards other cysteine proteinases such as cathepsins L,B and papain but had no effects on trypsin and pepsin. Both forms inhibited the processing of the enzymatically inactive proform of BCP (pro-BCP) to the activated mature BCP. BCPI alpha and BCPI beta shared many other features such as molecular mass determined by gel filtration, antigenicity, and HPLC profiles. NH(2)-terminal amino acid sequencing of the purified inhibitors revealed that three amino acid residues were different in the BCPI alpha and BCPI beta sequences, all others being identical. The hemolymph BCP inhibitor increased activity approximately four- to fivefold at the time of spinning and maintained this level of activity during pupation.

Proregion of Bombyx mori cysteine proteinase functions as an intramolecular chaperone to promote proper folding of the mature enzyme.

A cDNA encoding the proform of Bombyx cysteine proteinase (BCP) was expressed at a high level in Escherichia coli using the T7 polymerase expression system. The insoluble recombinant zymogen was solubilized and renatured by modifying a method applied to human pro-cathepsin L. Like the natural BCP precursor, the recombinant proenzyme was spontaneously converted to an active proteinase at pH 3.75. A deletion in the central region of the propeptide resulted in much loss of the activity, suggesting that the propeptide is essential for proper folding during renaturation. In contrast, the renatured mature form of recombinant BCP was not active but regained activity by including the propeptide in the renaturing buffer, suggesting that the propeptide, acting as an intramolecular chaperone, promotes refolding of the associated proteinase domain into an active conformation. The mature form of natural BCP rapidly lost its activity at neutral pH, whereas its proform was stable. The mature enzyme retained some activity in the presence of the propeptide. Arch.

Induction and inhibition of in vitro oocyte maturation and production of steroids in fish follicles by forskolin.

The effects of forskolin (FK) on in vitro oocyte maturation and production of steroids were examined in Oryzias latipes. When oocytes within preovulatory follicles were preincubated in the presence of FK for 2-10 hr, they matured normally after additional incubation for 10-20 hr in plain culture medium. Naked (follicle cell-free) oocytes did not mature under these conditions. FK stimulated dose-dependent production of steroids (estradiol-17 beta, E2, and 17 alpha,20 beta-dihydroxy-4-pregnen-3-one, 17 alpha,20 beta-diOHprog) and cAMP in follicle (granulosa) cells. On the other hand, exposure to FK within 2 hr after 17 alpha,20 beta-diOH prog stimulation caused reversible inhibition of gonadotropin (PMS)- or 17 alpha,20 beta-diOH prog-induced maturation of the intrafollicular oocytes in vitro. FK also significantly inhibited the 17 alpha,20 beta-diOHprog-induced maturation of naked oocytes, suggesting the existence of adenylate cyclase in fish oocytes. These data indicate that in Oryzias latipes, FK induces oocyte maturation by stimulating follicular production of maturation-inducing steroid (MIS), probably 17 alpha,20 beta-diOH prog, via an increase in cAMP, and that it may inhibit oocyte maturation by increasing ooplasmic cAMP and some inhibitory interaction between the granulosa cells and the oocyte through intercellular communication.