Molecular and Cellular Endocrinology 171 (2001) 111 – 117 Pan1b (17bHSD11)-enzymatic activity and distribution in the lung Phillip Brereton a , Takashi Suzuki b , Hironobu Sasano b , Kevin Li a , Carla Duarte a , Varuni Obeyesekere a , Francoise Haeseleer c , Krzysztof Palczewski c , Ian Smith a , Paul Komesaroff a , Zygmunt Krozowski a, * a Molecular Hypertension Laboratory, Baker Medical Research Institute, PO Box 6492, Melbourne 8008, Australia b First Department of Surgery and Pathology, Tohoku Uni6ersity, School of Medicine, Sendai, Japan c Department of Ophthalmology, Uni6ersity of Washington School of Medicine, Seattle, WA 98195 -6485, USA Abstract We describe a new member of the 17b-hydroxysteroid dehydrogenase group of enzymes. Human Pan1b displays greatest activity with 5a-androstan-3a,17b-diol (3a-Diol) as substrate, suggesting that it may be important in androgen metabolism. Enzymic activity was non-saturable with 3a-Diol but saturable with retinoids, although retinoids were not metabolized. Immunohistochemical studies on 10% formalin fixed and paraffin embedded sections of human tissues showed that Pan1b was present in acini and ciliated epithelia of the lung. In the fetus immuno reactivity was present in ciliated epithelia throughout gestation and staining appeared to be stronger in the second half of pregnancy. Pan1b was also expressed in the nonpigmented epithelium of the ciliary body, and in adrenocortical tumor cells. Although 3a-Diol is generally considered a degradation product of androgen metabolism it could have its own biological function. Pan1b may be an important modulator of the endocrine, or intracrine activity of this steroid. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: 17b-Hydroxysteroid dehydrogenase; Human lung; Androgens; Estrogens; 3a-Diol; Eye; Adrenal gland www.elsevier.com/locate/mce 1. Introduction Short chain alcohol dehydrogenases (SCAD) are a superfamily of enzymes involved in the metabolism of secondary alcohols and ketones. They are thought to have evolved from ancestral progenitors which metabo- lized sugars, but over time substrates have come to include polyols, antibiotics, organic acids, prostaglandins and steroids (Baker, 1991). Over one hundred members were recently identified in the public databases. A number of conserved domains can readily be identified by multiple alignment of protein sequences (Krozowski, 1994). The A domain, towards the N-ter- minus of the protein, contains the GXXXGXG motif and is known to bind the cofactor. Domains B and C are hydrophobic and form parallel beta sheets within the Rossmann fold. The B domain consists of the well conserved LVNNAG motif, while domain C contains a more variable GX(IV)(IV)X(IV)(SG)S sequence. Do- main D is the active site YXX(ST)K with absolutely conserved tyrosine and lysine residues. The presence of serine and threonine is also highly conserved at Y +1 and Y +3 and mutagenesis has shown that these residues determine the rate of catalysis (Obeyesekere et al., 1998). With the completion of the human genome project a vast amount of sequence data awaits assignment of biological function. Analysis of gene structure is facili- tated by knowledge of the corresponding messenger RNA species, usually derived from analysis of a specific cDNA. ESTs are short first pass sequences derived from sequencing random clones in a cDNA library. In the present study Expressed Sequence Tag (EST) data- bases with conserved motifs of the SCAD superfamily were searched to identify new members. Translation of the DNA sequences into all six read- ing frames and a search for residues conserved in the B domain yielded a cohort of putative SCAD members which were confirmed by searching for the C and D domains a set number of residues downstream. This approach produced several novel uncharacterized * Corresponding author. Tel.: 61-3-95224378; fax: +61-3- 95211362. E-mail address: zygmunt.krozowski@baker.edu.au (Z. Krozowski). 0303-7207/01/$ - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII:S0303-7207(00)00417-2