Kazuya Matsuura

Reduction of drug ketones by dihydrodiol dehydrogenases, carbonyl reductase and aldehyde reductase of human liver

In this study, we compared the enzymatic reduction of 10 drugs with a ketone group by homogeneous carbonyl reductase, aldehyde reductase and three dihydrodiol dehydrogenases of human liver cytosol. At least one and in some cases all of the three dihydrodiol dehydrogenases reduced each of the ten drugs. Among these naloxone, naltrexone, befunolol, ethacrynic acid and ketoprofen were substrates specific for the dehydrogenases. The other drugs--haloperidol, metyrapone, loxoprofen, daunorubicin and acetohexamide--were highly reduced by carbonyl reductase and/or aldehyde reductase. The dihydrodiol dehydrogenases also showed lower Km values for haloperidol and loxoprofen than did carbonyl reductase. The results indicate that the three dihydrodiol dehydrogenases, as well as the two reductases, are implicated in the reduction of ketone-containing drugs in human liver cytosol.

Switch of Coenzyme Specificity of Mouse Lung Carbonyl Reductase by Substitution of Threonine 38 with Aspartic Acid

Mouse lung carbonyl reductase, a member of the short-chain dehydrogenase/reductase (SDR) family, exhibits coenzyme specificity for NADP(H) over NAD(H). Crystal structure of the enzyme-NADPH complex shows that Thr-38 interacts with the 2′-phosphate of NADPH and occupies the position spatially similar to an Asp residue of the NAD(H)-dependent SDRs that hydrogen-bonds to the hydroxyl groups of the adenine ribose of the coenzymes. Using site-directed mutagenesis, we constructed a mutant mouse lung carbonyl reductase in which Thr-38 was replaced by Asp (T38D), and we compared kinetic properties of the mutant and wild-type enzymes in both forward and reverse reactions. The mutation resulted in increases of more than 200-fold in the Km values for NADP(H) and decreases of more than 7-fold in those for NAD(H), but few changes in the Km values for substrates or in the kcat values of the reactions. NAD(H) provided maximal protection against thermal and urea denaturation of T38D, in contrast to the effective protection by NADP(H) for the wild-type enzyme. Thus, the single mutation converted the coenzyme specificity from NADP(H) to NAD(H). Calculation of free energy changes showed that the 2′-phosphate of NADP(H) contributes to its interaction with the wild-type enzyme. Changing Thr-38 to Asp destabilized the binding energies of NADP(H) by 3.9-4.5 kcal/mol and stabilized those of NAD(H) by 1.2-1.4 kcal/mol. These results indicate a significant role of Thr-38 in NADP(H) binding for the mouse lung enzyme and provide further evidence for the key role of Asp at this position in NAD(H) specificity of the SDR family proteins.

Characterization of pulmonary carbonyl reductase of mouse and guinea pig.

Carbonyl reductases were purified from mouse and guinea pig lung. The mouse enzyme exhibited structural and catalytic similarity to the guinea pig enzyme: tetrameric structure consisting of an identical 23 kDa subunit; basicity (pI of 8.8); low substrate specificity for aliphatic and aromatic carbonyl compounds; dual cofactor specificity for NADPH and NADH; stereospecific transfer of the 4-pro S hydrogen of NADPH; and sensitivity to pyrazole, 2-mercaptoethanol and ferrous ion. Although 3-ketosteroids were extensively reduced by the mouse enzyme but not by the guinea pig enzyme in the forward reaction, the two enzymes similarly oxidized some alicyclic alcohols such as acenaphthenol, cyclohex-2-en-1-ol and benzenedihydrodiol in the presence of NADP+ and NAD+. A partial similarity between the two enzymes was observed immunologically, using antibodies against the purified guinea pig enzyme. The lung enzymes differ in several aspects from other oxidoreductases from extrapulmonary tissues. The immunoreactive protein was detected only in lung of the tissues of the two species.

Localization of Pulmonary Carbonyl Reductase in Guinea Pig and Mouse: Enzyme Histochemical and Immunohistochemical Studies'

We studied the localization of carbonyl reductase (E.C. 1.1.1.184) in guinea pig and mouse lung by enzyme histochemistry and immunohistochemistry, using antibodies against the guinea pig lung enzyme which crossreacted with the lung enzymes of both animals. Carbonyl reductase activity was detectable in the bronchiolar epithelial cells of small airways and in alveolar cells. In the immunohistochemical staining for carbonyl reductase, the reaction was strongest in the non-ciliated bronchiolar cells (Clara cells) and was weak in the ciliated cells and type II alveolar pneumocytes. Injection of a single dose of naphthalene led to significant impairment of carbonyl reductase activity and of microsomal mixed-function oxidase activities in mouse lung, with a marked decrease in both activity and immunoreactive staining in the bronchiolar epithelial cells. The results indicate that carbonyl reductase is localized primarily in the Clara cells, which are known to be sites of pulmonary drug metabolism.

Dihydrodiol dehydrogenases in guinea pig liver

Four major and four minor dihydrodiol dehydrogenases, with similar apparent molecular weights of 28,000 to 34,000 but with different charges, were purified from male guinea pig liver cytosol. One of the minor enzymes catalyzed only the oxidation of benzene dihydrodiol with a high Km value of 5.0 mM and was identified immunologically with aldehyde reductase. The other enzymes oxidized xenobiotic alicyclic alcohols and 17 beta-hydroxysteroids as well as benzene dihydrodiol. These enzymes exhibited higher affinity for 17 beta-hydroxysteroids than for alicyclic alcohols and benzene dihydrodiol, and immunologically cross-reacted with testosterone 17 beta-dehydrogenase purified from the same source. Four major enzymes and one minor with Km values for benzene dihydrodiol of about 0.2 mM, possessed specificity for 5 beta-androstane--17 beta-hydroxysteroids and dual cofactor requirement, whereas the other two minor enzymes with high Km values of over 5 mM showed apparent NADP and 5 alpha-androstane specificity. The dihydrodiol dehydrogenase activity was localized in the cytosol of liver. The results indicate that the hepatic oxidation of dihydrodiols in the guinea pig is mediated by cytosolic testosterone 17 beta-dehydrogenase isozymes and aldehyde reductase. Testosterone 17 beta-dehydrogenase immunologically identical to the liver enzymes was detected only in kidney, whereas aldehyde reductase was detected in all tissues of the guinea pig.

Cloning and sequencing of the cDNA species for mammalian dimeric dihydrodiol dehydrogenases.

Cynomolgus and Japanese monkey kidneys, dog and pig livers and rabbit lens contain dimeric dihydrodiol dehydrogenase (EC 1.3.1.20) associated with high carbonyl reductase activity. Here we have isolated cDNA species for the dimeric enzymes by reverse transcriptase-PCR from human intestine in addition to the above five animal tissues. The amino acid sequences deduced from the monkey, pig and dog cDNA species perfectly matched the partial sequences of peptides digested from the respective enzymes of these animal tissues, and active recombinant proteins were expressed in a bacterial system from the monkey and human cDNA species. Northern blot analysis revealed the existence of a single 1.3 kb mRNA species for the enzyme in these animal tissues. The human enzyme shared 94%, 85%, 84% and 82% amino acid identity with the enzymes of the two monkey strains (their sequences were identical), the dog, the pig and the rabbit respectively. The sequences of the primate enzymes consisted of 335 amino acid residues and lacked one amino acid compared with the other animal enzymes. In contrast with previous reports that other types of dihydrodiol dehydrogenase, carbonyl reductases and enzymes with either activity belong to the aldo-keto reductase family or the short-chain dehydrogenase/reductase family, dimeric dihydrodiol dehydrogenase showed no sequence similarity with the members of the two protein families. The dimeric enzyme aligned with low degrees of identity (14-25%) with several prokaryotic proteins, in which 47 residues are strictly or highly conserved. Thus dimeric dihydrodiol dehydrogenase has a primary structure distinct from the previously known mammalian enzymes and is suggested to constitute a novel protein family with the prokaryotic proteins.

Expression of mRNAs for Dihydrodiol Dehydrogenase Isoforms in Human Tissues

Dihydrodiol dehydrogenase (DD) [EC 1. 3. 1. 20] catalyzes the NADP+-linked oxidation of /trans-dihydrodiols of polycyclic aromatic hydrocarbons to corresponding catechols, and controls the formation of both their carcinogenic dihydrodiol epoxides (Oesch, et al.,, 1984) and cytotoxic o-quinones through autoxidation of the catechol metabolites (Flowers, et al.,., 1996). In addition, DD in mammalian liver is implicated in the metabolism of xenobiotic carbonyl compounds, steroids and prostaglandins because of its broad substrate specificity (Penning, et al.,, 1986; Hara, et al.,, 1986; Ohara, et al.,, 1994; 1995).

Separation and properties of multiple forms of dihydrodiol dehydrogenase from hamster liver.

1. Five multiple forms of dihydrodiol dehydrogenase (EC 1.3.1.20) with similar molecular weights of around 35,000 were purified from hamster liver cytosol. 2. All the enzymes oxidized trans-dihydrodiols of benzene and naphthalene and reduced various carbonyl compounds, but showed clear differences in specificities for other alcohols and cofactors, and in inhibitor sensitivity. 3. Two NADP+-dependent enzymes were immunologically identified with aldehyde reductase (EC 1.1.1.2) and 3 alpha-hydroxytsteroid dehydrogenase (EC 1.1.1.50). 4. The other enzymes with dual cofactor specificity oxidized xenobiotic alicyclic alcohols, and one of them was active on 3 alpha- and 17 beta-hydroxysteroids with NAD+ as a preferable cofactor.

Subcellular distribution and properties of carbonyl reductase in guinea pig lung

On subcellular fractionation, carbonyl reductase (EC 1.1.1.184) activity in guinea pig lung was found in the mitochondrial, microsomal, and cytosolic fractions; the specific activity in the mitochondrial fraction was more than five times higher than those in the microsomal and cytosolic fractions. Further separation of the mitochondrial fraction on a sucrose gradient revealed that about half of the reductase activity is localized in mitochondria and one-third in a peroxidase-rich fraction. Although carbonyl reductase in both the mitochondrial and microsomal fractions was solubilized effectively by mixing with 1% Triton X-100 and 1 M KCl, the enzyme activity in the mitochondrial fraction was more highly enhanced by the solubilization than was that in the microsomal fraction. Carbonyl reductases were purified to homogeneity from the mitochondrial, microsomal, and cytosolic fractions. The three enzymes were almost identical in catalytic, structural, and immunological properties. Carbonyl reductase, synthesized in a rabbit reticulocyte lysate cell-free system, was apparently the same in molecular size as the subunit of the mature enzyme purified from cytosol. These results indicate that the same enzyme species is localized in the three different subcellular compartments of lung.

Purification and properties of two multiple forms of dihydrodiol dehydrogenase from guinea-pig testis.

NADP+-dependent dihydrodiol dehydrogenase (trans-1,2-dihydrobenzene-1,2-diol: NADP+ oxidoreductase, EC 1.3.1.20) activity in the cytosol of guinea-pig testis was separated into two major and two minor peaks by Q-Sepharose chromatography; one minor form was immunologically cross-reacted with hepatic aldehyde reductase. The two major enzyme forms were purified to homogeneity. One form, which had the highest amount in the tissue, was a monomeric protein with a molecular weight of 32,000 and isoelectric point of 4.2, showed strict specificity for benzene dihydrodiol and NADP+, and reduced pyridine aldehydes, glyceraldehyde and diacetyl at low rates. Another form, with a molecular weight of 36,000 and isoelectric point of 5.0, oxidized n-butanol, glycerol and sorbitol as well as benzene dihydrodiol in the presence of NADP+ or NAD+, and exhibited much higher reductase activity towards various aldehydes, aldoses and diacetyl. The pI 5.0 form was more sensitive to inhibition by sorbinil and p-chloromercuriphenyl sulfonate than the pI 4.2 form and was activated by sulfate ion. The two enzymes did not catalyze the oxidation of hydroxysteroids and xenobiotic alicyclic alcohols and were immunologically different from hepatic 17 beta-hydroxysteroid-dihydrodiol dehydrogenase. The results indicate that guinea-pig testis contains at least two dihydrodiol dehydrogenases distinct from the hepatic enzymes, one of which, the pI 5.0 enzyme form, may be identical to aldose reductase.