Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adrenergic regulation of the pineal enzyme serotonin N-acetyltransferase [arylalkylamine N-acetyltransferase (AA-NAT); EC 2.3.1.87] accounts for the circadian rhythm in melatonin formation. In the present study, the role of protein phosphatases in the adrenergic regulation of rat pineal AA-NAT was investigated using specific inhibitors. In cultured pineals, the serine/threonine phosphatase type 1 and type 2A inhibitors okadaic acid and calyculin A significantly decreased adrenergically or cAMP-induced AA-NAT activity, whereas the serine/threonine phosphatase type 2B inhibitor cypermethrin and tyrosine phosphatase inhibitor dephostatin were ineffective. Reverse transcriptase-polymerase chain reaction (RT-PCR) data indicate that okadaic acid exerts its effect on cAMP-dependent AA-NAT induction by downregulating the amount of AA-NAT transcript. The 'third' messengers, inducible cAMP early repressor (ICER) and Fos-related antigene-2 (Fra-2), are believed to play a negative role in pineal AA-NAT transcription. Okadaic acid increased the cAMP responsiveness of neither ICER mRNA nor Fra-2 mRNA. Therefore, the regulatory role of pineal serine/threonine phosphatases in adrenergically stimulated AA-NAT expression probably does not depend on ICER or Fra-2.
 ...
PMID:Serine/threonine phosphatase inhibitors decrease adrenergic arylalkylamine n-acetyltransferase induction in the rat pineal gland. 1144 72

Luteinizing hormone (LH) influences the secretion of melatonin (N-acetyl-5-methoxytryptamine) from the pineal gland. The present study examined the possible presence of LH/chorionic gonadotropin (CG) receptor in the pineal gland of adult female rats. Reverse transcriptase-polymerase chain reaction analyses demonstrated that LH/CG receptor mRNA is expressed in the pineal gland. Western blotting showed that the pineal gland, like the ovary, contains an 80 kDa receptor protein. Immunohistochemistry revealed that LH/CG receptor, arylalkylamine N-acetyltransferase (a regulatory enzyme in melatonin biosynthesis) and serotonin (a melatonin precursor) are localized primarily to the same cells of the pineal gland. We further found that the levels of pineal LH/CG receptor protein in normal cycling female rats change significantly during the estrous cycle, being lowest at early metestrus. These results demonstrate that LH/CG receptor is expressed in the pineal gland, primarily in melatonin-synthesizing cells, namely pinealocytes. Furthermore, it is suggested that LH influences pineal melatonin secretion through binding to this receptor. In addition, LH/CG receptor levels in the pineal gland are regulated during the estrous cycle under normal physiological conditions.
 ...
PMID:Expression of luteinizing hormone/chorionic gonadotropin receptor in the rat pineal gland. 1684 39

Melatonin (N-acetyl-5-methoxytryptamine) prevents oxidative stress-induced cataract development, and previous studies have suggested that the ocular lens synthesizes melatonin. In the present study, we examined whether two key enzymes in melatonin biosynthesis, arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole-O-methyltransferase (HIOMT), are expressed in the lens of adult male rats. Reverse transcriptase-polymerase chain reaction analyses demonstrated that both AANAT and HIOMT mRNAs are expressed in the lens. Western blotting for AANAT protein showed that the lens, like the pineal gland, contains this enzyme protein with a molecular mass of 24 kDa. Immunohistochemistry revealed that AANAT protein is localized to the lens cortical fiber cells. Serotonin, which is a substrate for AANAT and a melatonin precursor, was also found in this region. These findings demonstrate that the lens expresses AANAT and HIOMT, and suggest that the cortical fiber cells are the main melatonin-synthesizing sites in the lens. Locally synthesized melatonin in the lens cortical fiber cells may protect the lens itself from cataract development.
 ...
PMID:Expression and cellular localization of melatonin-synthesizing enzymes in the rat lens. 1719 43