Cholesterol side-chain cleavage enzyme

Cholesterol side-chain cleavage enzyme is commonly referred to as P450scc, where "scc" is an acronym for side-chain cleavage. P450scc is a mitochondrial enzyme that catalyzes conversion of cholesterol to pregnenolone. This is the first reaction in the process of steroidogenesis in all mammalian tissues that specialize in the production of various steroid hormones.

P450scc is a member of the cytochrome P450 superfamily of enzymes (family 11, subfamily A, polypeptide 1). The gene name is CYP11A1.

Nomenclature

The systematic name of this enzyme class is cholesterol,reduced-adrenal-ferredoxin:oxygen oxidoreductase (side-chain-cleaving). Other names include:

Tissue and intracellular localization

The highest level of the cholesterol side-chain cleavage system is found in the adrenal cortex and the corpus luteum. The system is also expressed at high levels in steroidogenic theca cells in the ovary, and Leydig cells in the testis. During pregnancy, the placenta also expresses significant levels of this enzyme system. P450scc is also present at much lower levels in several other tissue types, including the brain. In the adrenal cortex, the concentration of adrenodoxin is similar to that of P450scc, but adrenodoxin reductase is expressed at lower levels.

DySPAN

The Dynamic Spectrum Access Networks (DySPAN) standards committee, formerly Standards Coordinating Committee 41 (SCC41), and even earlier IEEE P1900 Standards Committee, is sponsored by the Institute of Electrical and Electronics Engineers (IEEE). The group develops standards for radio and spectrum management. Its working groups and resulting standards, numbered in the 1900 range (starting with 1900.1), are sometimes referred to as IEEE 1900.X.

Background

The IEEE P1900 Standards Committee was established in March 2005 jointly by the IEEE Communications Society (ComSoc) and the IEEE Electromagnetic Compatibility Society (EMC). The effort developed supporting standards for radio and dynamic spectrum management.

On March 22, 2007 the IEEE Standards Board approved its reorganization as Standards Coordinating Committee 41 (SCC41), Dynamic Spectrum Access Networks (DySPAN). The IEEE ComSoc and EMC sponsored this effort, as they did for IEEE 1900. The IEEE 1900 Committee ceased to exist at the inaugural meeting of SCC41 in April 2007. The work of the IEEE 1900.x Working Groups continued under SCC41. SCC41 voted to be directly answerable to ComSoc in December 2010, and was renamed as IEEE DySPAN-SC. At its December 2010 Meeting, the IEEE Standards Association Standards Board (SASB) approved the transfer of projects to the Communications Society Standards Board.

Roland SC-55

The Roland SC-55 (Sound Canvas) is a GS MIDI sound module released in 1991 by Roland. The SC-55 was the first sound module to incorporate the new General MIDI standard.

The SC-55 used both PCM and a cut-down version of the LA synthesis engine, to support 24-voice polyphony with 16-part multitimbrality. It came preloaded with the Roland MT-32's variation bank, but lacked the MT-32's re-programmability. Aimed at PC music enthusiasts, the SC-55 featured 317 instrument patches, including the GS drum kits and additional controllers. The selection of effects includes reverb and chorus.

Alongside the SC-55, Roland released the SB-55 (Sound Brush), an inexpensive MIDI sequencer module the same size as the Sound Canvas. Both the Sound Canvas and Sound Brush could be rackmounted alongside each other.

Other models with comparable tone generators include Roland CM-300, Roland CM-500 and Roland SC-155 sound modules. CM-300 and CM-500 models lack the LCD screen and extended controls of SC-55. Both models have external appearance nearly identical to Roland's earlier CM-32/64-series modules. SC-155 adds additional slider controls for master and channel level and panning. Additionally, CM-500 includes fully SysEx compatible LA tone generator similar to CM-32L's.